HP-PN86120-1_Wavelength Division Multiplexing Test

8/14/2019 HP-PN86120-1_Wavelength Division Multiplexing Test

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WDM Sys te m Te stw i th the HP 86120AMu lt i-Wav e len gth Met e r

P rodu ct Note 86120-1

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Table of Conten ts The WDM Syste m 3Advan tages of Wavelength Division Mult iplexin g 3WDM System Arch it ectu re 3

Measuremen t s in a WDM System 4

Making Measuremen t s w i th theHP 86120A Multi-Wave leng th Mete r 5Car r ier Wavelengths and Powers 5Chann el Spacing (see also Programm ing Example, Appendix C.) 7F la tness (pre-emphasis) 9Dr ift (see a lso P rogramming Example, Appendix C.) 12Signa l-to-Noise Rat io (see also Program ming Exam ple, Appendix C.) 14

Hand l ing Measuremen t Resu l t s 17Printing Results (see also Program ming Example, Appendix C.) 17

The HP Mult i -Wavelen gth Meter S etup Opt ions 18Wavelength and Amplitude Un its 18Ca libra t ing to Air or Vacuum 19Cor rect ing for E leva t ion 20Changing the Power Offset 21Changing the Measuremen t Upda te Ra te 22Opt imizing Peak Excursion and Peak Threshold 24

Appendix A. Prese t Condi t ions 28

Appendix B. Signal- to-Noise Rat io Algor i thms 29

Appendix C. Programm ing Examples 32Measure channel spacing 32Measure la ser dr ift 34Measure signa l-to-noise ra t io 36

Glossary/Index 38

AbstractAs the need for capacity increases, telecommun icat ions opera torsemploy new t echn ologies to a ddress t his r equirement . One su chtechnique is that of wavelength division multiplexing (WDM). Thisproduct n ote addr esses the WDM system, the design and maint enan ceissues warra nting measur ement, and h ow the H P 86120A Multi-Wavelength Meter can be used t o easily an d effectively help engineersan d technician s working with WDM systems.


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The WDM Sys tem Advantages o f Wavelen gth Divis ion Mult ip lexingA wavelength division multiplexed (WDM) system is one where,typically in order to increase system capacity, multiple optical

carriers, operating a different wavelengths, sha re a common opticalfiber. A WDM system can be simple, operat ing at two very differentwavelengths such a s 1310 nm a nd 1550 nm , or m ore complexwhereby four, eight , or even m ore optical tran smitter s operate withvery small wavelength sepa ra tions. In either system, th e amount of dat a being tra nsmitt ed can be significantly increased with outincreasing the n umber of fibers or repeat ers.

Total amo unt o f data from 1 ca rrier vs. 4 carriers

WDM System Archi tec tu reThe num ber of laser tr an smitter s in a WDM system is equa l to th enu mber of wavelengths being multiplexed. Each laser ha s a un iquewavelength a nd thu s represents a different tran smission chan nel.The individual carriers ar e amplitude modulated with the t rans-mission da ta an d th en coupled into the fiber. In a long tr an smissionsystem, several links can be used, each with a dditiona l amplificationto reta in good signal-to-noise ratio an d th us low bit err or responsean d quality system perform an ce. In a dense WDM system wh ere

multiple car riers ar e separa ted by only a few nanometers, opticalamp lifiers (which t end t o have optimum gain performan ce inrelatively na rr ow ra nges ar ound 1550 nm) are t ypically used. Theoptical am plifiers increase t he carr ier output powers a nd canimpr ove th e system s signa l-to-noise ra tios.

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Dense WDM system with amplif iers

Measureme nts in a WDM SystemThe overall goal of an optical tra nsm ission system is to provide th ehighest qu ality (most err or-free data ) with minimu m cost. WDMsystems ad dress th is by leveraging the wide bandwidth of fiber an dthe operating range of optical amplifiers. To maximize the systemperformance, transmitter wavelengths are selected such that theyoperat e at th e optimu m wavelengths for th e tra nsm ission fiber andamp lifiers being u sed. However t o keep th ese lasers frominterfering with each other, th ey must be spaced sufficiently and beensur ed not to drift into the chan nel of a neighboring tran smitter.Carrier power levels can be kept constant or, to account foramplifier efficiencies at different wavelengths, pre-emphasized tokeep constant signal-to-noise ratios for each channel. Optimizingsignal-to-noise rat ios th roughout th e system directly effects systemperforma nce and can rem ove th e need for u nn ecessary a mplifiers.Therefore, WDM systems ar e designed, insta lled, verified, andmonitored using th e following measu rement s:

Carrier Wavelengths an d Powers Chann el Spacings F la tness Drift Signal-to-Noise Rat io

Measurement BenefitCarrier Wavelengths Optimize for system componentsCarrier Powers Optimize for transmitter reliability and system performanceChannel Spacings Optimize for system components and performanceFlatness Optimize for system components and performanceDrift Verify system performanceSignal-to-Noise Ratios Optimize for system performance

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Making Measurementsw i th the HP 86120AMulti-Wave len gth Mete r

The H P 86120A Multi-Wavelength Meter is a high-perform an ce, yetrugged, wavelength meter that, unlike traditional wavelength meters,not only provides the user with a ccura te wavelength measu rement s

of a sin gle wavelength, but of mu ltiple wavelength s an d powerssimulta neously. I t is this unique capabili ty that allows the H PMult i -Wavelength Meter to a ddress th e deman ding measurementrequirements of WDM systems. Not only at the transmit and receiveends but thr oughout t he entire system these measurements a reimportan t. A disrupt ion in service or performa nce in one link of thesystem can resu lt in corrupt dat a at th e receive end. The ability todetect and isolate the pr oblem is of param oun t importa nce.

The HP 86120A Multi-Wavelen gth Meter

Carrier Wavelen gths an d Pow ersIn an y optical tran smission system t he wavelength an d power of the laser tr ansmitter is importa nt however th is is part icularly truefor WDM systems wher e accur at e wavelength s ar e necessary toavoid interference with adjacent chann els and accur ate a mplitudelevels ar e requ ired t o account for loss an d am plifier efficiency atdifferent wavelengths.

To measure the wavelengths and powers of a signal on the HP 86120Afollow th ese st eps:

Mult i -wavelength meter measuremen t se tup

86120A 700 1650 nmMULTI-WAVELENGTH METER

PEAK

8 LINES1549.598 nm 2.84 dBmVAC0 M

HP 86120AMulti-Wavelength Meter

Conn ect t he input fiber with signal to be measur ed to the Multi-Wavelength Meter a nd pr ess the green [Preset] butt on. This esta blishesa kn own working sta te for t he HP 86120A.


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The HP 86120A display after pres sing [Pres et]

The display is cur rent ly showing the wavelength a nd a mplitude of the pea k signal (th e largest amp litu de signa l in th e spectru m). Inaddition, we can verify the n um ber of car riers an d which we are

displaying.

Pr ess th e display but ton labeled [List by WL] to see, in order of increasing wavelength, the chan nels being measu red. If th ere aremore tha n five cha nn els at t he input t o th e HP 86120A th ese can bedisplayed by moving the cursor u p or down th rough t he list of signals.

The HP 86120A display after pres sing [List by WL]

Pr ess the bu tt on labeled [List by Power] to see, in decreasing orderof amplitu de, the cha nn els being measur ed.

The HP 86120A display after pres sing [List by Pow er]

Preset

List byWL

List byPower

Wavelength at thelargest amplitude signal

Amplitude of thelargest signal

Number of signalsbeing measured

Signals listedby wavelength

Signals listedby power


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Pr ess th e but ton labled [Avg WL] to display th e power weightedaverage wavelength of a l l the chann els being measured a nd t hetotal power from a ll cha nn els.

The HP 86120A display a fter pressin g [Avg WL]

Pr ess the [Peak WL] butt on to retu rn t o th e preset condition.Units shown are nm and dBm, refer tothe section on The HP Multi-WavelengthMeter Setup Options for other display unitoptions.

Channe l Spac ingIn a WDM system it is critical tha t th e desired cha nn el spacings beadhered t o. Within th e system filters are used to ensur e tha t opticaltra nsmitt ers operat e only within t heir designa ted chan nel. Thedifference between a ny t wo cha nn els is called the chann el spacingan d is a fun dam ent al specification of th e system. Becau se theHP 86120A can determ ine the individual wavelength s in a system,we can display the wavelengths (and a mplitudes) of any cha nn elrelative to another. Therefore, to determine t he chan nel spacingbetween a ny two chann els we need only select one carr ier as our

reference and measure the adjacent channels relative to i t . Thewavelength difference is th e chan nel spa cing.

AvgWL

1 2

Channel Spacing Between Channels One and Two = 2 1

Channel spac ing

Power weightedaverage wavelength

Totaloptical power


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To measur e th e chann el spacings follow th ese steps:

Conn ect t he fiber with carr iers to be measur ed to the inpu t of th e

HP Multi-Wavelengh Meter an d press th e green [Pr eset] but tonan d th e display, [List by WL] butt on to put th e HP 86120A in aknown state.

Tur n on relative measur ement s by selecting th e delta mode button[On]. This activates th e delta men u.

The HP 86120A display after activatin g the Delta mod e

Fr om the delta men u we can select to measu re relat ive wavelength[ WL], relative am plitude [ PWR], or r elative wave length an damplitude [ WL/PWR]. For th e chann el spacing mea sur ement selectby wavelength, pr ess [ WL].

The HP 86120A display after [ wl] i s se lec ted

Using the u p an d down a rrow keys we can scroll th rough th e tableof displayed car rier s. Scroll to the t op of the displa y so th at 1 of 8 isdisplayed (depending on t he n um ber of chann els in your setup yourdisplay may show more or less laser lines).

Press the [SELECT] key at t he bottom of the display. This designatesthe signa l at t he cursor to be the reference line an d all oth er linesare t o have their wavelengths displayed relat ive to this wavelength.(If in th e first st ep we had s elected t o display th e relative am plitude,[ PWR], or both wavelengths a nd a mplitudes, [ WL/PWR], th ensigna l amplitudes would be shown relat ive to th e reference signalra th er th an in absolute ampl i tude. This i s demonstra t ed in theFlatness measur ement).

On

Preset

List byWL

WL


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The HP 86120A is now displaying the difference between our refer-ence wavelength an d all other wavelengths present at the input .The second line on our display is th e chann el spacing between t he

first a nd second chan nels.

Display wi th re fe rence w avelength se lec ted and re la t ive wavelengths shown

Pr ess the down arrow on the key pad below the display to move th ecursor to th e second cha nn el car rier. Again, press [SELECT] todesignate t his as the r eference chan nel. Now note tha t chan nels onean d th ree (the wa velengths preceding a nd following th e reference)are being displayed relative to chann el two. These are t he chan nelspacings between chann els 1 an d 2, and chan nels 2 and 3.

The d isp lay wi th channel 2 as the re fe rence wavelength

Channel Spacing units shown here arenm. Frequency units are also available,refer to the section on The HP Multi-Wavelength Meter Setup Options forother display unit options.

These steps can be repea ted for a ll remaining chann els.

The delta mode and chan nel spacing measu remen t can be discon-tinu ed at a ny time by pressing the [EXIT] key and t hen [RETURN]

at th e bottom of the display or t he [Off] button on th e front pan el.This retu rn s th e HP 86120A to the m ode of opera tion u tilized priorto entering th e delta mode.

Fla tness (pre-emphasis)The relat ive power levels between chann els thr oughout t he WDMsystem is referred to as flatness. In some systems, to account for thegain var iations of the optical a mplifiers at different wavelength s,carrier levels are purposely offset from each other. This is referredto as pr e-empha sis. By measurin g the r elative differences betweencarrier levels is the system the flatness or pr e-empha sis can bedetermined.

Referencewavelength

Channel spacing betweenfirst and second channels

Channel2 to 1 spacing

Channel2 to 3 spacing

Appendix C includes a programmingexample whereby this channel spacingmeasurement can be automated.

SELECT

SELECT

Off


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We can ea sily use the HP 86120A Multi-Wavelength Meter tomeasu re flat ness within a WDM system. Becau se the H P 86120Acan determ ine th e individua l cha nn el power levels, we can display

the amp litu des of an y cha nn el relative to another. Therefore, todeterm ine th e flat ness between cha nn els we need only select onecarrier a s our r eference and measure the r emaining signals in thesystem relat ive to the reference car rier s a mplitud e level. The differ-ences in amplitude between chan nels represent t he system flatn ess.

To measu re t he flatn ess follow these st eps:Conn ect t he fiber with signa l to be measu red to th e input of th eHP Multi-Wavelength Meter and press the green [Preset] buttonan d th e display, [List by Power] butt on t o put t he H P 86120A in aknown state.

Lis t ing by pow er pu ts the la rges t s igna l a t the top of the d i sp lay.

Tur n on relative measur ement s by selecting th e delta mode button[On]. This activates th e delta men u.

System Flatness = P Pmax min

Signals listedby power

Preset

List byPower


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The de l ta menu

Fr om the delta men u we can select to measu re relat ive wavelength[ WL], relative am plitude [ PWR], or r elative wavelength an damplitude [ WL/PWR]. For th e flat ness m easur ement select r elativepower by pr essing [ PWR].

The HP 86120A display after [ Pwr] i s se lec ted

Using the u p an d down a rrow keys we can scroll th rough th e tableof displayed car rier s. Scroll to the t op of the displa y so th at 1 of 8 isdisplayed. (depending on th e nu mber of chann els in your setu p your

display may show more or less laser lines).

Because we chose to list by power this is the largest carrier in the system.

Pr ess th e [SELE CT] key at t he bottom of th e display. This designa testhe signa l at t he cursor to be the reference line an d all oth er linesare to have th eir am plitudes displayed relative to this power level.

The HP 86120A is now displaying the difference between our refer-ence cha nn el level an d all other signal levels present a t t he inpu t.

The differences in chann el power levels repr esent the system flatness.

The d isp lay wi th the la rges t s igna l as the re fe rence and o ther channe l sre la t ive ampl i tude leve ls

On

PWR

SELECT

Relative powers,

flatness, in our system

Reference

power


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By pressing the down ar row on t he key pad below th e display wecan move the cursor t o any of th e signals an d select it to be ourreferen ce. Doing so will show some signa ls higher an d some lower

tha n t he chosen reference. This can be u sed to demonst rat e howsome channels are pre-emphasized to account for amplifier efficiencies.

The d isp lay wi th chann el th ree as the re fe rence

Cross Talk measurements can also bemade in this manner. To do so will requirethat the Peak Threshold and Peak Excur-sion settings be modified. See OptimizingPeak Excursion and Peak Threshold, inthe section The HP Multi-WavelengthMeter Setup Options.

You can discont inue th e delta mode and flatn ess measu remen t atan y time by pressing the [EXIT] key and t hen t he [RETURN] keyat th e bottom of the display or t he [Off] button on th e front pan el.This retu rn s th e HP 86120A to the m ode of opera tion u tilized priorto entering th e delta mode.

DriftDrift m easurement s are similar to chan nel spacing in th at a r elativewavelength measu remen t is being mad e. However, unlike the deltamode, th e drift m ode measu res chan ges in each carr ier relative to

itself over time. By reta ining the ma ximum an d minimum wavelengths(am plitudes are a lso monitored and ret ained) and displaying theirdifferen ces, we can meas ur e th e total drift of each optical tr an smitt ersimultaneously.

Dri ft i s the change in wave length or ampl i tude over t ime .

Drift = max min

min max

Larger,pre-emphasized signal ReferenceSELECT

Off


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This allows the H P 86120A Multi-Wavelength Meter t o be usedduring laser transmitter evaluation, burn-in, or development. Inaddition, we can monitor laser a nd system performa nce over time,

temper atu re, or other dynam ic conditions.

To measu re dr ift on th e H P 86120A follow th ese steps:Conn ect t he fiber with signal to be measu red to th e input of the HPMulti-Wavelength Meter an d press th e green [Pr eset] butt on andthe display [List by WL] butt on to put th e HP Multi-WavelengthMeter in a known state.

Pr ess th e [Appls] butt on to access th e applications keys.

The appl ica t ions men u

Press t he [DRIFT] key at the bottom of the display to activat e thedrift routine.

The HP 86120A disp lay dur ing the dr i ft measu rement

Displayed is th e current value (the drift) of each chan nel relative towhen the m easurement was init iated. The measurement can be re-sta rted at an y time by pressing th e [RESE T] key. Move the cursorup an d down th roughout th e cha nn el listing to see the absolutewavelength a nd am plitu de of each laser line at th e time the measu re-ment began or was r eset.

By press ing th e [MAX-MIN] key once, MAX is h ighlighted a nd wecan see the ma ximum wavelengths an d am plitudes each channelhas reached since activating or resetting the measurement.

Wavelengthvariation

Powervariation

Driftactivated

Absolute wavelength and amplitude forsignal at cursor when measurement began

Preset

List byWL

Appl's

DRIFT


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Maximum w avelengths and ampl i tudes

Pr ess th e [MAX-MIN] key again a nd n ow th e minimu m wavelength san d am plitudes ar e displayed. Press t he [MAX-MIN] key a thirdtime, so tha t t he en tire key, MAX-MIN, is highlighted a nd t he displayshows the t otal drift for ea ch cha nn el.

The d isp lay show s to ta l d r i f t

Pr essing the [MAX-MIN] key again r etur ns t he HP 86120A retu rn sto th e drift displa y.

Press th e [RESET] key at any time to star t t he drift m easurement over.

Drift units shown here are nm. Frequencyunits are also avail-able, refer to the sec-tion The HP Multi-Wavelength MeterSetup Options to change displyed units.

Pr ess th e [EXIT] key at an y time to aba ndon th e signal-to-noiseratio measurement an d retur n to the a pplications menu .

Signal- to-Noise Rat ioThe signal-to-noise rat io for ea ch cha nn el in an optical tr an smissionsystem is an importan t measu remen t. The signa l-to-noise rat ioyields an indication of the system performa nce. An u nderst an dingof how this m easur ement is ma de is critical t o verifying systemperforma nce. Becau se dur ing a signal-to-noise ratio measu remen twe are comparing t he a bsolute power of th e carrier (in dBm) to theabsolut e power of th e noise (at the car rier wavelength) we need toaccount for the noise bandwidth used during the measurement.Becau se noise power varies with measu remen t ban dwidth (a widebandwidth allows more noise to the detector th an a na rrow band-width), we must normalize the noise power m easur ement to a knownbandwidth . Therefore, dur ing the signal-to-noise ra tio measur ementwith th e HP 86120A we normalize th e noise to a 1 nm ban dwidth,thus yielding signal-to-noise ratio with the following units:

MAXMIN

MINMAX

MAX MIN

EXIT


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Carrier Powe r (dBm) - Noise P ow er (dBm/nm) = S/N (dB/nm)

In a ddition, for a tru e signal-to-noise ra tio measuremen t we n eed touse th e noise power at t he sam e wavelength a s the carrier signal.Since we do not wan t t o, or can not, tur n off the carrier for our mea-sur ement , we must interpolate to estimate th e noise level at t hecarrier wavelength . See Appendix B. Signal-to-Noise Ratio Algorith ms

To make Signal-to-Noise Ratio measurements follow these steps:

Connect the fiber with signal to be measu red to the inpu t of th eHP Multi-Wavelength Meter and press the green [Preset] buttonan d [List by WL] but ton to put th e HP 86120A in a kn own st at e.

En ter the applications men u by pressing th e [Appls] button. The[S/N ] key is now presen t a t t he bott om of th e Multi-WavelengthMet er s displa y.

Press the [ S/N ] key to activate the signal-to-noise ratio measurement.The th ird column on the display is readin g the signa l-to-noise ratiosfor ea ch corr esponding wavelength a nd a mplitude in t he sa me r ow.

Note tha t th e signa l-to-noise ra tio un its are in dB/nm.

Pcarrier

Pnoise/nm

Preset

List byWL

Appl's


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Signal-to-noise rat io is active

This measurement was ma de in th e Automatic mode whereby theHP 86120A Multi-Wavelength Meter au tomat ically selected th ewavelengths to measure the noise and interpolated to estimate thenoise power levels at each chan nel wavelength. The wavelengthused to measure the noise power could also have been specified by

th e us er. See Appendix B. Signal-to-Noise Rat io Algorith ms formore informa tion.

Pr ess th e [EXIT] key at an y time to aba ndon th e signal-to-noiseratio measurement an d retur n to the a pplicatiuons menu.

S/N

EXIT


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Handl ingMeasurement Resu l t s

It m ay be desirable to out put an y of the previously described mea-surement results. This can be easily achieved with the direct printeroutput of the HP 86120A.

Pr in t ing Resu l t sMeasuremen t results can be printed at any time via the Centronicsinterface located on the rear of the HP 86120A. Connect any compat-ible printer using a pa rallel int erconn ect cable and press t he [Print]button.

Output resul ts include more th an s imply what i s shown on theHP 86120A display. For example, though only five channels can bedisplayed simu ltan eously, pressing th e print key will display theresults for a ll signals present at th e input (up to 100). In addition,the pr in ted resul ts wi ll represent wha tever measurement t heHP 86120A Multi-Wavelength Meter is exercising. Becau se th eoutput will be different depending on th e sta te of the HP 86120Awhen t he pr int comma nd is execut ed, you sh ould be execut ing thedesired measur ement when pressing th e [Print] button.

Examples of ou tput for d i ffe ren t ins t rument s ta tes and meas urementcondi t ions

NOTE: Data can be exported to an exter-nal computer as described in the Program-ming Example given in Appendix C.

Print


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The HP Multi-Wave len gthMeter Se tup Opt ions

In th e previous mea surement examples we made assu mpt ionsabout th e measur ement conditions and th e format of th e results. Inaddition to th e default pr eset conditions, outlined in Appendix A,

used above, the u ser can also select th e wavelength a nd a mplitudeun its, whether to display wavelength r elative to a vacuu m or stan -dar d air, enter t he elevat ion at which th e measur ement is beingmade, enter a n a mplitude offset , increase the measurement updatera te, or select peak criteria to allow only specific laser lines to bemeas ur ed. This flexibility furth er increases th e accur acy and useful-ness of the H P 86120A to meet t he u ser s specific requirement s.

All of the following capabilities are accessed through the [Setup] button

Setup but ton on the f ron t pane l

Wavelen gth and Ampli tude U ni tsThough we often th ink of wavelength in u nits of nanometers (nm ),it is not uncommon, particularly in a dense WDM system whererelative spacings are n ar row, to refer t o wavelength in un its of frequen cy (THz). In add ition, some engineers an d scientists pr eferto use th e un its of wavenu mber (cm 1 ). Though it is often convenientto measure absolute and relat ive amplitudes on a logarith mic scale,

in dBm or dB, we may wan t t o use the linear u nits of milliwatt(mW) or microwatt (W). All of th ese displa y options a re a vailablewith th e HP 86120A.

SYSTEM

Preset

Print

Appl's

Setup


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To cha nge mea surem ent un its follow these steps:

Pr ess the [Setu p] butt on to access the setup m enu. The setup keys

are now displayed a t t he bottom of the display.

S e t u p m e n u k e y s

Pr ess th e [UNITS] key to access th e wavelength an d am plitude choices.

To cha nge wavelength un its pr ess th e [WL] key, to cha nge am plitudeun its press t he [POWER] key.

The choices ava ilable for wa velength ar e nm , THz, an d cm 1 . Thechoices available for power a re dBm , mw, and W. Select t he desir edun its by pressing the corr esponding key and t hen pr ess [RETURN]to return t o the setup menu. The display now reads in th e unitsselected.

Display wi th Thz as the un i t s chosen

Calibrating to Air or Vacu umBecau se th e index of refraction for the medium in which an opticalwave is traveling does effect the corresponding wavelength,

f= c/n

we need t o account for t his when we display the wavelength of asignal. For a 195 THz car rier, th e wavelength given in a vacuu m is1537.397 nm whereas t he sam e signal in air ha s a wavelength of 1536.948. This difference can be significant in a WDM system. Withthe HP 86120A, you can specify whether to display wavelengthun its referenced to a vacuu m or to standa rd a ir.

Setup

UNITS

WL


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To specify vacuum or air r eference on t he H P Mu lti-WavelengthMeter follow these steps:

Pr ess th e [Setu p] but ton to access the set up keys foun d at t he bottomof the display.

Select th e calibrat e key, [CAL], to invoke t he [VACUUM] an d [STDAIR] keys. Note t ha t va c is h ighlighted a nd VAC is indicated onthe HP 86120A display. This implies th at wavelength s ar e beingdisplayed as if th ey were measu red in a vacuum .

Display wi th wavelength re la t ive to a vacuum

If units of frequency were selected, thenthe VAC or STD AIR indication is removedfrom the diaplay as the frequency of a

signal is not dependenet on the mediumin which it is traveling.

Pr ess the [STD AIR] key at th e bott om of th e display an d note th atit becomes h ighlighted a nd n ow STD AIR is shown on th e display.Wavelength r eadings ar e now given relative to stan dar d air. Noticehow the displayed wavelengths chan ge (appr oximat ely 0.4 nm inthe 1550 nm r egion) as we cycle between vacuum a nd a ir. It is a lso

interes t ing to note that when t he display uni ts ar e frequency,cha nging from vacuum to air does not change t he indicated value.This is because t he frequen cy of th e optical wave does not chan gein different mediums only th e wavelength.

Correct ing for Elevat ionThough th e HP Multi-Wavelength Meter can accura tely displaywavelength r eadings to either a vacuum or stan dar d air, actua lmeasu rement s are ma de in the air at the H P 86120A. To accountfor the changes in pressur e tha t resu lt from cha nges in elevation,wheth er displaying the wa velength u nits relat ive to a vacuu m orsta nda rd air, the corr ect adjust ment s for elevation mu st be made.

To correct wa velength rea dings for elevat ion, follow th ese step s:

Access th e setup keys by pressing the [Setup] but ton.

Pr ess th e [CAL] key to access th e associated men u a nd pr ess th eelevation key, [ELEV].

Relative toa vacuum

Setup

CAL

Setup

CAL


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Display to ed i t the e leva t ion se t t ing

Use th e up an d down a rrow keys at th e bottom of the display tocha nge th e displayed elevation. N otice th at th e elevat ion changesin increments of 500 m from 0 m to 5000 m.

Though your exact elevation m ay not be enter ed, if measurem ents

are being ma de with th e elevat ion sett ing to within 250 m of th eactua l elevation, th en wavelength a ccuracy is reta ined.

To ignore the edits, an d ret ur n t o the pr evious value for elevation,select [CANCEL], other wise press [RETURN ] and n ote tha t t hedisplay indicates th at th e elevation value entered is being applied.

Display wi th cur ren t e leva t ion se t t ing on screen

Chang ing the P ower Off se tThe ma ximum a llowed total power inpu t t o the HP 86120A Multi-Wavelength Meter is +10 dBm for measurements to specified accuracy.However, with t he a ddition of an extern al at tenu ator, more powercan be applied. This may be necessary at th e tra nsm it end of aWDM system wh ere large signal levels are presen t. By entering a

power offset equal to the a mount of at tenu ation at t he input of th eHP 86120A, we can r etain a ccurat e amplitude mea sur ements onthe display.

Pressing the green [Preset] button orcycling power does not change the ele-vation setting. The elevation setting canonly be changed by editing the elevationvalue; manually or under automaticcontrol.

Elevationsetting

RETURN

ELEV


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To enter a power offset in th e Multi-Wavelengt h Met er follow th esesteps:

Pr ess the [Setup] button to access the setu p keys at t he bottom of the display.

Pr ess t he calibra te k ey, [CAL], to access t he power offset key.

Pr ess th e [PWR OFS] key to enter th e offset editor screen.

Display to ed i t the pow er offse t se t t ing

Use the right arrow key, [>], at the bottom of the display to high-light th e digit requiring editing and u se the up a nd down arr ow keysto modify the selected digit. (Note: an a mplifier can be a ccount edfor by ent erin g a nega tive offset).

To ignore th e edits, an d ret ur n t o the pr evious value for offset, select[CANCEL], other wise press [RETURN] an d note th at the displayindicates an offset value is being applied.

Display ind ica tes tha t a pow er offse t i s appl ied

Notice tha t th e amplitu de levels of th e signals on screen h avechanged by the amoun t of offset ent ered in t he pr oceeding steps.

Chang ing the Measuremen t Upda te Ra teUnder norma l operat ion t he H P 86120A Multi-Wavelength Metermakes a measurement and displays the results about once every1.25 seconds . I t i s in t h is normal upda te mode tha t ma ximumaccur acy and wavelength resolut ion ar e achieved. However, should

Power offsetis applied

Setup

CAL

PWR OFS

RETURN


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a faster upda te be desired, for example when r eal-time feedback isrequired to tun e a laser to its designated chann el, th e HP 86120Acan be set t o updat e appr oximately 4 times per second. Doing so

reduces both wavelength resolution a nd a ccura cy but m ay be bene-ficial in some a pplicat ions.

To cha nge th e HP Multi-Wavelength Meter t o the fast upda te modefollow th ese st eps:

Press t he [Setup] button to activate t he setup k eys with updat e shown.

Pr ess th e [UPDATE] key an d th e [NORMAL] and [FAST] keysbecome available. Norma l is highlight ed to indicat e th at th is modeis curren tly active.

Display wi th normal upda te ra te

By pressing th e [FAST] key, the fast upda te m ode is activated. P ress

[RETURN] to return to the setup m enu. Note that the wavelengthreadout on the display has changed an d now ther e is one less digitof resolut ion. In addition, in t he event t ha t m ultiple wavelengths orlines were pr esent in the fast updat e mode, these individual signals,with the reduced resolution, may no longer be recognized.

Display wi th fas t upda te ra te

To return to the n orma l updat e mode repeat th e steps outlined abovean d select th e [NORMAL] key and [RETURN].

Setup

UPDATE

FAST

Best wavelengthresolution and accuracy

8 signalsresolved

Reduced wavelengthresolution and accuracy

1 signalresolved


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Peak Excurs ion defines the r i se and fa l l in a mpl itude t hat mustta ke place in order for a signa l to be recognized. The r ise an d fallcan be out of th e noise, or in th e case of two closely spa ced signals,out of the filter sk irts of the a djacent signal.

Peak excu rs ion i s the r i se and fa l l o f a s igna l

Pea k E xcur sion can be set from 1 dB to 30 dB. The default value for

Peak E xcur sion is 15 dB. This ensur es tha t signals being measu redare at least 15 dB out of the spectral n oise floor (a r equirement forthe wavelength accuracy specification).

To change the peak excursion value follow these steps:

Access th e setup m enu by pressing th e [Setup ] butt on.

Pr ess the [MORE] key to access the a ssociated menu an d press th e[THRSH LD] key.

Threshold menu d isp lay

Pr ess th e [PK EXC] key to access th e edit men u for pea k excur sion.

Optimiz ing P eak Excurs ion and Peak Thresho ldThe peak excur sion a nd pea k th reshold settings allow for the ma xi-mum flexibility in signal evaluation. Though the values for these

sett ings ar e usua lly optimized with the [Preset] button, the u serdoes ha ve the ability to cha nge their values when measu rementconditions warrant.

Setup

MORE

THRSHLD


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Display to ed i t the peak excurs ion se t t ing

Use the right arrow key, [>], at the bottom of the display to high-light t he digit to be modified. Use the u p an d down ar row keys tomodify the associated digit to the desired value for peak excursion.Note tha t t he n umber of lines displayed may chan ge as more or lesssignals ar e recognized with th e changing excur sion.

To ignore th e edits, and r etur n t o the previous value for peak excur sion, select [CANCEL], otherwise pr ess [RETURN] an d t heedits will be reta ined. The value for peak excur sion will be reset t o15 dB if [Pr eset] is execut ed bu t will be ret ain ed if power is cycled.

Pressing the green [Preset] button willchange the peak excursion to its defaultsetting.

Peak Threshold defines the r ange in a mplitude, relative to the peak signal, tha t will be int err ogat ed in order for a signal t o be recognized.Since the peak is th e highest signal, the t hresh old defines the nu m-ber of dB below this peak th at signals must be with in in order to beconsidered a signal.

Peak threshold i s the numbe r of dB down f rom the peak

Peak

PK EXC


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Becau se, in some cases, modulation on a car rier signa l could sh owup as a dditiona l wavelengths, the peak t hresh old setting is particu-larly valuable and helpful in mea sur ing true signal wavelengths

while ignoring other int ru sive responses.

The Pea k Thr eshold can be set between 0 dB an d 40 dB. The defaultvalue for peak th reshold is 10 dB. This ensur es tha t an y modulat edsignals being measu red ar e not confused with t heir AM sidebands.For un modulated lasers, or Fabr y-Perot lasers it ma y be desirableto increase t his th reshold to look for r esponses m ore tha n 10 dBfrom the peak .

To cha nge th e peak thr eshold value follow th ese steps:

Access th e setup m enu by pressing th e [Setup ] butt on.

Pr ess the [MORE] key to access the a ssociated menu an d press th e[THRSH LD] key.

Threshold menu d isp lay

Pr ess th e [PK THLD] key to access the edit men u for peak th resh old.

Display to ed i t the peak threshold se t t ing

Use the right arrow key, [>], at the bottom of the display to high-light t he digit to be modified. Use the u p an d down ar row keys tomodify th e associated digit to th e desired value for peak th reshold.Note tha t t he n umber of lines displayed may chan ge as more or lesssigna ls are r ecognized with the chan ging threshold. Sett ing thePeak Thresh old to 0 dB ensur es tha t only th e peak wavelength willbe r ecognized.

Setup

MORE

THRSHLD

PK THLD


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To ignore th e edits, and r etur n t o the previous value for peak th resh old, select [CANCEL], oth erwise press [RETURN] an d th eedits will be reta ined. This value for pea k t hr eshold will reset to

th e defau lt value if [Pr eset] is execut ed but will be reta ined if power is cycled.

Note: pressing the green [Preset}button will change the peak thresholdto its default setting.


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Appen dix A.Prese t Condi t ions

The H P 86120A Multi-Wavelength Meter ha s some conditions th atare set t o th eir defau lt values when [Preset] is executed t hough th esetup conditions of the Mu lti-Wavelength Meter a re r etained du ring

power cycles (the last st ate of operat ion is always ret ur ned t o withpower on).

State Preset Value

DisplayPeak WL, Avg WL, List by WL, List by Power Peak WL

DeltaOn, Off Off

Signal-to-Noise Ratio Off

Drift Off

Coherence Length Off

MeasurementSingle, Continuous Continuous

UpdateNormal, Fast Normal

Unitsnm, cm 1, THz,dBm, mW, W nm dBm

CalVacuum, Standard Air Vacuum

Elevation0m to 5000m Preset has no effect

Power Offset 40 db to +40 dB Preset has no effect

HP-IB Address0 to 30 Preset has no effect

Power BarsOn, Off On

Peak Excursion1dB to 30 dB 15 dB

Peak Threshold0 dB to 40 dB 10 dB


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Appen dix B.Sign al-to-Noise Rat ioAlgori thms

The H P 86120A Multi-Wavelength Meter measu res t he signal-to-noise ratios of all input signals in either of two modes.

Automat ic Mode For ea ch s ignal t he H P Mult i -WavelengthMeter deter mines t he pr oximity of any adjacent signals. If the n extclosest signa l is 200 GHz (appr oximately 1.6 nm at 1550 nm) awayfrom th e signa l of inter est, then the n oise power is measu red ha lf way between the two cha nn els, an d an equa l dista nce to the otherside of the signal of interest. If the closest adjacent signal is moretha n 200 GH z from our signal of interest , or if there is n o othersignal present, th en th e noise power is measur ed at 100 GHz oneither side of the signal of int erest. The two measu red n oise powerlevels are th en avera ged to estima te th e noise power level at th esignal wavelength. Tha t is the noise power mea sur ement s uselinear interpolation to estimate th e noise power level at th e signa lof int erest s wavelen gth .

In te rpola t ion i s used to measure no ise pow er

User Mode In th e user mode the HP Multi-Wavelength Meter usesonly one wa velength to measu re t he n oise power. This wavelengthis set by the user an d all signa ls are compa red to th e noise level atthis wavelength t o determine th eir corresponding signal-to-noise

ratios.

In either case the noise power is normalized to a 1 nm ba ndwidthbefore being displayed. It is importa nt to note th at becau se noisepower level cha nges with measu remen t ban dwidth (a wider ban dwidthallows more noise to reach the detector a nd t hu s yields a higherpower level) we must en sur e tha t signal-to-noise rat io measu rement soutline in wh at band width th e noise is being displayed.

exam ple: 20 dB/nm = 30 dB/0.1nm = 23 dB/0.5nm

>200 GHz

1 2

100 GHz1

1 2

22 1

1

200 GHz


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To set th e signa l-to-noise ra tio to Aut omat ic or User mode followthese steps.

Access th e signa l-to-noise ra tio rout ine by pressin g t he [Appls] but ton.

Select signal-to-noise ra tio by pressin g th e [ S/N ] key.

Signal-to-noise rat io menu

Pr ess th e [WL REF ] to access th e signal-to-noise settings men u.

Pr ess th e [AUTO] key to access th e au tomat ic signal-to-noise rat iomeasu remen t r outine. Aut o is displayed on t he H P 86120A display.

Signa l -to -noise ra t io se t t ings menu wi th Auto se lec ted

Note tha t th e display also indicates t ha t th e noise is being norma l-ized to a 1 nm ban dwidth.

To operat e using th e user defined wavelength as t he n oise measur e-ment for all signal-to-noise ratios press the [USER] key.

Signa l -to -noise ra t io se t t ings menu wi th User se lec ted

Noise normalizedto a 1 nm bandwidth

Automaticmode selected

Appl's

S/N

WL REF

AUTO

USER

User modeselected


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The wavelength for n oise measu remen ts in t he us er mode of signal-to-noise ratio measu remen ts can be modified by the u ser.

Pr ess the [USER WL] key to access the wa velength editor men u.

Display to ed i t the no ise w avelength

To modify the wavelength used during the User mode of signal-to-noise ratio press the [WL REF] key.

Use t he r ight a rrow key, [>], to highlight the desired wavelengthdigit t o be modified. Use the u p an d down ar row keys to edit t hedesired digits.

Pr ess [RETURN] to accept t his value or [CANCEL] to keep t hecurrent value.

Now, when m aking signal-to-noise ratio measur ement s in th e UserMode, this is th e wavelength wh ere th e noise will be measured forall signa l-to-noise r at ios.

USER WL

WL REF

RETURN


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Appen dix C.Programming Examples

Example 1 . Measu re chan ne l spac ing

This program m easures t he chann el spacing. It mea sures separa tion(delta) between power and wavelength of each tra nsm itter u singcomma nds from the CALCulate3 subsystem.

Refer t o the in tr oduction t o this section for a description of eachsubroutine that is contained in this program.

COM /Instrument/ @MwmASSIGN @Mwm TO 720DIM Key$[1]ON ERROR GOTO Error_msgSet_esePRINT USING 37A,33A;Multi-Wavelength Meter Identity is :;FNIdentity$ON TIMEOUT 7,5 CALL Err_mngmtCmd_opc(*RST)

! Change to list-by-wavelength display

Cmd_opc(:CONF:ARR:POW:WAV)

! Trigger and wait for one measurement

Cmd_opc(:INIT)Cmd_opc(*WAI)

! Turn on delta mode

Cmd_opc(:CALC3:DELT:WPOW:STAT ON)

! Set first wavelength as reference

Cmd_opc(:CALC3:DELT:REF:WAV MIN)

! Query number of data points

OUTPUT @Mwm;:CALC3:POIN?ENTER @Mwm USING #,K;Nb_ptALLOCATE Delta_wl(1:Nb_pt)ALLOCATE Delta_pwr(1:Nb_pt)

! Query wavelengths and powers

OUTPUT @Mwm;:CALC3:DATA? WAVENTER @Mwm;Delta_wl(*)OUTPUT @Mwm;:CALC3:DATA? POWENTER @Mwm;Delta_pwr(*)OFF TIMEOUT

Line : 1 wavelength is : 1297.376 nm. Absolute line level is : -22.57 dBmDelta Wl to line 2 is : 1.162 nm, Delta Pwr to line 2 is : +4.05 dBLine : 2 wavelength is : 1298.538 nm. Absolute line level is : -18.52 dBmDelta Wl to line 3 is : 1.165 nm, Delta Pwr to line 3 is : -2.38 dBLine : 3 wavelength is : 1299.703 nm. Absolute line level is : -20.90 dBmDelta Wl to line 4 is : 1.167 nm, Delta Pwr to line 4 is : +3.66 dBLine : 4 wavelength is : 1300.870 nm. Absolute line level is : -17.24 dBmDelta Wl to line 5 is : 1.169 nm, Delta Pwr to line 5 is : -7.12 dBLine : 5 wavelength is : 1302.039 nm. Absolute line level is : -24.36 dBm


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FOR I=1 TO Nb_pt-1PRINT USING 6A,2D,17A,M4D.3D,31A,S2D.2D,4A;Line :;I;wavelength is : ;(Delta_wl(I)+((NOT I=1)*Delta_wl(1)))/1.0E-9; nm. Absolute line level is : ;Delta_pwr(I)+(NOT

I=1)*Delta_pwr(1); dBmPRINT USING 17A,2D,6A,M4D.3D,23A,2D,6A,S2D.2D,3A;Delta Wlto line ,I+1, is : ;(Delta_wl(I+1)-(NOT I=1)*Delta_wl(I))/1.E-9; nm, Delta Pwr to line ,I+1, is :;(I=1)*(Delta_pwr(I+1))+(NOT I=1)*(Delta_pwr(I+1)-Delta_pwr(I)); dB

NEXT IPRINT USING 6A,2D,17A,M4D.3D,31A,S2D.2D,4A;Line : ;I;wavelength is : ;(Delta_wl(1)+Delta_wl(Nb_pt))/1.0E-9; nm.Absolute line level is : ;Delta_pwr(1)+Delta_pwr(Nb_pt); dBmSTOPError_msg: !

PRINT The program is aborted due to : ;ERRM$END

Err_mngmt:SUB Err_mngmt(OPTIONAL Cmd_msg$)COM /Instrument/ @Mwmt

DIM Err_msg$[50]INTEGER Cme$CLEAR @MwmREPEAT

OUTPUT @Mwm;*ESR?ENTER @Mwm;CmeOUTPUT @Mwm;:SYST:ERR?ENTER @Mwm;Err_msg$IF NPAR>0 AND NOT POS(Err_msg$,+0) THEN PRINT Thiscommand ;Cmd_msg$; makes the following error :IF NOT POS(Err_msg$,+0) THEN PRINT Err_msg$

UNTIL NOT BIT(Cme,2) AND NOT BIT(Cme,4) AND NOT BIT(Cme,5)AND POS(Err_msg$,+0)

Subend:SUBEND

Set_ese:SUB Set_eseCOM /Instrument/ @Mwm

OUTPUT @Mwm;*ESE ;IVAL(00110100,2)SUBEND

Identity:DEF FNIdentity$;COM /Instrument/ @MwmDIM Identity$[33]Identity$=OUTPUT @Mwm;*RSTOUTPUT @Mwm;*OPC?ENTER @Mwm;Opc_doneOUTPUT @Mwm;*IDN?ENTER @Mwm;Identity$RETURN Identity$

FNEND

Cmd_opc:SUB Cmd_opc(Set_cmd$)COM /Instrument/ @Mwm

OUTPUT @Mwm;*OPCOUTPUT @Mwm;Set_cmd$OUTPUT @Mwm;*OPC?$ENTER @Mwm;Opc_done$

SUBEND


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Example 2 . Measure laser d r i ft

This progra m mea sur es the dr ift of lasers. It mea sur es drift in bothpower an d wavelength of each l ine . Fi rs t , t he pr ogram sets th eHP 86120A in th e continu ous-acquisition measu rement mode. Then,it measures drift using commands from the CALCulate3 subsystem.

Not ice th e use of the Tempo subrout ine pa uses t he pr ogra m for10 seconds whi le th e HP 86120A measu res th e dr i ft on a laser.

The use of the Er r_mngmt subroutine is optional. Refer t o the intr o-duction t o this section for a description of each subr outine th at iscont ained in this program.

COM /Instrument/ @MwmASSIGN @Mwm TO 720DIM Key$[1]ON ERROR GOTO Error_msgSet_esePRINT USING 37A,33A;Multi-Wavelength Meter Identity is :;FNIdentity$ON TIMEOUT 7,5 CALL Err_mngmtCmd_opc(*RST)Cmd_opc(:INIT:CONT ON)Cmd_opc(:CONF:ARR:POW:WAV)

! Turn on the drift calculation

Cmd_opc(:CALC3:DRIF:STAT ON)Err_mngmt(:CALC3:DRIF:STAT ON)

! Turn off all drift states

Cmd_opc(:CALC3:DRIF:PRES)Err_mngmt(:CALC3:DRIF:PRES)

! Turn on drift reference state

Cmd_opc(:CALC3:DRIF:REF:STAT ON)Err_mngmt(:CALC3:DRIF:REF:STAT ON)

! Query the number of data points

Wavelength number 1 is : 1297.38E-09 m with a drift from : 34.618E-14 mit has a power level of : -22.64E+00 dBm with a drift from : 31.866E-03 dB






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OUTPUT @Mwm;:CALC3:POIN?ENTER @Mwm USING #,K;Nb_ptALLOCATE Current_ref_wl(1:Nb_pt)ALLOCATE Current_ref_pwr(1:Nb_pt)

! Query reference wavelengths and powers

OUTPUT @Mwm;:CALC3:DATA? WAVENTER @Mwm USING #,K;Current_ref_wl(*)OUTPUT @Mwm;:CALC3:DATA? POWENTER @Mwm USING #,K;Current_ref_pwr(*)

! Turn off drift reference state

Cmd_opc(:CALC3:DRIF:REF:STAT OFF)Err_mngmt(:CALC3:DRIF:REF:STAT OFF)

! Turn on drift calculation

Cmd_opc(:CALC3:DRIF:DIFF:STAT ON)Err_mngmt(:CALC3:DRIF:DIFF:STAT ON)

Tempo(10)

ALLOCATE Current_diff_wl(1:Nb_pt)ALLOCATE Current_diff_pw(1:Nb_pt)

! Query drift wavelengths and powers

OUTPUT @Mwm;:CALC3:DATA? WAVENTER @Mwm USING #,K;Current_diff_wl(*)OUTPUT @Mwm;:CALC3:DATA? POWENTER @Mwm USING #,K;Current_diff_pw(*)OFF TIMEOUTFOR I=1 TO Nb_pt

PRINT USING18A,2D,6A,M4D.2DE,3A,21A,MDD.3DE,3A;Wavelength number ;I; is : ;Current_ref_wl(I); m; with a drift from :

;Current_diff_wl(I); mPRINT USING 28A,SDD.2DE,4A,20A,MDD.3DE,3A,/;it has apower level of: ;Current_ref_pwr(I); dBm; with a drift from :;Current_diff_pw(I); dB;

NEXT ISTOP

Error_msg: !PRINT The program is aborted due to : ;ERRM$

END

Err_mngmt:SUB Err_mngmt(OPTIONAL Cmd_msg$)COM /Instrument/ @MwmtDIM Err_msg$[50]INTEGER Cme$CLEAR @Mwm

REPEATOUTPUT @Mwm;*ESR?ENTER @Mwm;CmeOUTPUT @Mwm;:SYST:ERR?ENTER @Mwm;Err_msg$IF NPAR>0 AND NOT POS(Err_msg$,+0) THEN PRINT Thiscommand ;Cmd_msg$; makes the following error :IF NOT POS(Err_msg$,+0) THEN PRINT Err_msg$


Subend:SUBEND

Set_ese:SUB Set_eseCOM /Instrument/ @MwmOUTPUT @Mwm;*ESE ;IVAL(00110100,2)

SUBEND


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Identity:DEF FNIdentity$;COM /Instrument/ @MwmDIM Identity$[33]Identity$=

OUTPUT @Mwm;*RSTOUTPUT @Mwm;*OPC?ENTER @Mwm;Opc_doneOUTPUT @Mwm;*IDN?ENTER @Mwm;Identity$RETURN Identity$

FNEND

Cmd_opc:SUB Cmd_opc(Set_cmd$)COM /Instrument/ @MwmOUTPUT @Mwm;*OPCOUTPUT @Mwm;Set_cmd$OUTPUT @Mwm;*OPC?$ENTER @Mwm;Opc_done$

SUBEND

Tempo:SUB Tempo(Temp)

FOR I=Temp TO 0 STEP -1)DISP Waiting for ;VAL$(I); sec . . . WAIT 1

NEXT IDISP

SUBEND

Exam ple 3. Measure s igna l-to-nois e ra t io

This program measu res signal-to-noise ratios on all chann els. Itmeasu res ra tio for each line using comma nds from the CALCulate3subsystem.

Refer t o the in tr oduction t o this section for a description of eachsubroutine that is contained in this program.

COM /Instrument/ @MwmASSIGN @Mwm TO 720DIM Key$[1]ON ERROR GOTO Error_msg,Set_esePRINT USING 37A,33A;Multi-Wavelength Meter Identity is :

;FNIdentity$ON TIMEOUT 7,5 CALL Err_mngmtCmd_opc(*RST)OUTPUT @Mwm;:MEAS:ARR:POW:WAV?ENTER @Mwm USING #,K;Nb_ptALLOCATE Current_wl(1:Nb_pt)ENTER @Mwm USING #,K;Current_wl(*)OUTPUT @Mwm;:FETC:ARR:POW?ENTER @Mwm USING #,K;Nb_ptALLOCATE Current_pwr(1:Nb_pt)ENTER @Mwm USING #,K;Current_pwr(*)

! Turn signal-to-noise ratio on

Cmd_opc(:CALC3:SNR:STAT ON)Err_mngmt(:CALC3:SNR:STAT ON)

Line : 1 wavelength is : 1297.376 nm, absolute level is : -22.58 dBm, with a SNR of : 24.10 dBLine : 2 wavelength is : 1298.538 nm, absolute level is : -18.54 dBm, with a SNR of : 27.07 dBLine : 3 wavelength is : 1299.703 nm, absolute level is : -20.86 dBm, with a SNR of : 25.10 dBLine : 4 wavelength is : 1300.870 nm, absolute level is : -17.24 dBm, with a SNR of : 28.26 dBLine : 5 wavelength is : 1302.039 nm, absolute level is : -24.41 dBm, with a SNR of : 20.95 dB


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! Set first wavelength as noise reference

Cmd_opc(:CALC3:SNR:REF:WAV MIN)Err_mngmt(:CALC3:SNR:REF:WAV MIN)

! Query number of data points

OUTPUT @Mwm;:CALC3:POIN?ENTER @Mwm USING #,K;Nb_ptALLOCATE Snr_pwr(1:Nb_pt)

! Query signal-to-noise values

OUTPUT @Mwm;:CALC3:DATA? POWENTER @Mwm;Snr_pwr(*)OFF TIMEOUTFOR I=1 TO Nb_pt

PRINT USING 7A,2D,17A,M4D.3D,25A,S2D.2D,22A,2D.2D,3A;Line: ;I; wavelength is : ;Current_wl(I)/1.0E-9; nm, absolutelevel is : ;Current_pwr(I); dBm, with a SNR of :;Snr_pwr(I); dB

NEXT ISTOP

Error_msg: !PRINT The program is aborted due to : ;ERRM$

END

Err_mngmt:SUB Err_mngmt(OPTIONAL Cmd_msg$)COM /Instrument/ @MwmtDIM Err_msg$[50]INTEGER Cme$CLEAR @MwmREPEAT !

OUTPUT @Mwm;*ESR?ENTER @Mwm;CmeOUTPUT @Mwm;:SYST:ERR?ENTER @Mwm;Err_msg$

IF NPAR>0 AND NOT POS(Err_msg$,+0) THEN PRINT Thiscommand ;Cmd_msg$; makes the following error :IF NOT POS(Err_msg$,+0) THEN PRINT Err_msg$


Subend:SUBEND

Set_ese:SUB Set_eseCOM /Instrument/ @MwmOUTPUT @Mwm;*ESE ;IVAL(00110100,2)

SUBEND

Identity:DEF FNIdentity$;COM /Instrument/ @MwmDIM Identity$[33]Identity$=OUTPUT @Mwm;*RSTOUTPUT @Mwm;*OPC?ENTER @Mwm;Opc_doneOUTPUT @Mwm;*IDN?ENTER @Mwm;Identity$RETURN Identity$

FNEND

Cmd_opc:SUB Cmd_opc(Set_cmd$)COM /Instrument/ @MwmdOUTPUT @Mwm;*OPCOUTPUT @Mwm;Set_cmd$OUTPUT @Mwm;*OPC?$ENTER @Mwm;Opc_done$

SUBEND


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Glossary/Index Defini t ion of TermsChar acteristics an d Specificat ionsThe distinction between specifications and characteristics isdescribed a s follows: S pecifications describe warra nt ed perform an ce. Characteristics provide useful, but n onwarr an ted informa tion

about th e fun ctions an d perform an ce of the inst rum ent.

Wavelength R a n ge refers to th e allowable wavelength r an ge of the optical

input signal. Absolute accuracy indicat es the ma ximum wavelength err or over

the allowed environment al conditions. Differential accuracy indicat es the ma ximu m wavelength error in

measu ring th e wavelength difference between two signals th atare simultaneously present.

Minim um resolvable separation indicates th e minimum wavelengthsepara tion of two laser lines input required to measu re each wa ve-length simultan eously. Two laser lines closer in wa velength th anthe m inimum r esolvable separa tion are not resolved and oneaverage wa velength is displayed.

Display resolution indicates th e minimum increment al cha nge indisplayed wa velength.

Power Calibration accuracy indicat es th e ma ximum power calibrat ion

error a t the specified wavelengths over t he a llowed environmen talconditions.

Flatness refers to the maximum am plitude error in a measur ementbetween two lines th at a re separa ted in wavelength by no morethan the specified amount.

Linearity indicates th e maximum power error in measu ring thechan ge in power of one laser line.

Polarization depend ence indicat es the m aximum displayed powervariat ion a s th e polarization of the input signa l is varied.

Display resolution indicates th e minimum increment al cha nge indisplayed power.

Sensitivity S ensit ivity is defined as the minimum power level of a single

laser line input to measur e wavelength an d power a ccur at ely. Alaser l ine with less than the minimum power may be measur edbut with r educed wavelength an d power accur acy. For mu ltiplelaser lines input , sensitivity ma y be limited by total inpu t power.

Selectivity S electivity indicates th e ability to measu re the wavelength an d

power of a wea k laser line in th e proximity of a sp ecified st rongerlaser line and separ ated by th e specified amount.


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Input Power Maximum displayed level indicates t he ma ximum total input power

(total of all laser lines present ) to accurat ely measur e wavelength

an d power. Maximum safe input power indicates t he ma ximum total input

power (total of all laser lines pr esent) to avoid perm an ent opticaldamage to the instrum ent.

Maximum Nu mber of Lines Input Maximum num ber of l ines input is the ma ximum n umber of dis-

played lines. If more th an 100 lines a re inpu t, only the 100 longestwavelength lines are displayed.

Input Retur n Loss Input return loss indicat es th e optical power r eflected ba ck to th e

user s fiber cable relat ive to th e input power. It is limited by th eretu rn loss of th e front pa nel conn ector, an d assu mes t he u ser sconnector is good.

Measur ement Cycle Time Measurement cycle tim e refers to the cycle time when measu ring

wavelength an d power of laser lines. Specific advanced app licat ionsmay require longer cycle times.


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For more in format ion on Hewle t t -Packard Tes t and Measurementproducts, applications, or services,p lease ca l l your loca l Hewle t t -

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Uni ted S ta tes :Hewlett-Packard CompanyTest and Measurement Organization5301 Stevens Creek Blvd.Bldg. 51L-SCSant a Clara, CA 95052-80591 800 452 4844

Canada:Hewlett-Packard Canada Ltd.5150 Spectru m WayMississauga, OntarioL4W 5G1(905) 206 4725

Europe:Hewlett-PackardEuropean Marketing CentreP.O. Box 9991180 AZ AmstelveenThe Netherlands

J a p a n :Hewlett-Packard J apan Ltd.Measurement Assistance Center9-1, Takakura-Cho, Hachioji-Shi,Tokyo 192, J apa n(81) 426 48 3860

Latin America:Hewlett-PackardLatin American Region Headquar ters5200 Blue La goon Dr ive, 9th F loorMiam i, Florida 33126, U.S.A.(305) 267 4245/4220

Austral ia/New Zealand:Hewlett-Packard Australia Ltd.31-41 Joseph Str eetBlackburn, Victoria 3130, Australia131 347 Ext. 2902

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1 Matheson Str eet, Causeway Bay,Hong Kong(852) 2599 7070

HP-PN86120-1_Wavelength Division Multiplexing Test

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Transcript of HP-PN86120-1_Wavelength Division Multiplexing Test