8/2/2019 1211_3594

1/4

Application Note 1211

Telecommunications

Several schools utilize distance learning to meet demands for greater variety in theircurriculum. Distance learning entails transmitting a presentation or lecture from onelocation to several remote locations for students to observe.

Distance learning offers several benefits to the traditional classroom setting. It providesfor a more effective use of an educators time, and allows a specialist's expertise to bespread across a wider audience. In addition, distance learning permits the sharing of

resources between institutions and increases the availability of a broader curriculum tothe student body. In short, distance learning solves educators problem of providingmore variety with fewer resources.

Several networks, such as DS3, analog or DS1/fractional DS1, exist to facilitate distancelearning. Of these, a DS3 network proves to be the best solution. Due to the availabilityof greater bandwidth, a DS3 network requires less signal compression than a DS1network. This leads to a higher quality video signal with DS3 transmission than withDS1. Because DS3 transmission requires less compression than DS1, DS3 compressionequipment costs significantly less, making the DS3 network a more cost-effective videotransmission solution.

DS3 video transmission also compares favorably to analog video transmission. Analog

transmission distance limitations arise because an analog signal repeater amplifies boththe signal and any noise accompanying the signal; a digital signal can be effectivelyregenerated without amplifying the accompanying noise. This advantage allows a digitalsignal to be successfully transmitted over longer distances. In addition, analog videotransmission requires an analog switch, which is not normally found in a central office.Digital cross-connect systems provide DS3 switching and are frequently available as anintegral part of the telephone company network. Therefore, digital video transmissionutilizes existing switching capabilities whereas analog video transmission requirespurchasing additional switching equipment, making digital video transmission a morecost-effective solution.

DS3 FLC Distance Learning

8/2/2019 1211_3594

2/42

DS3 FLC Distance Learning Application Note 1211

ADC offers the DS3 Fiber Loop Converter (FLC) as an effective solution for DS3 videotransmission. A DS3 FLC system consists of two identical modules interconnected by apair of singlemode fibers capable of transmitting a standard DS3 rate video signal. TheDS3 FLC module converts a DS3 electrical input signal into an optical output signal andconverts an optical input signal back into a DS3 electrical output signal. Two separatefiber cables, one for each direction of transmission, provide full duplex communications.The modules are configured in either a 1 + 1 protection mode or as a single non-

protected system. In the protection mode, a standby protect system, consisting of anadditional DS3 FLC module at each location connected by an additional fiber pair,provides system redundancy. Failures affecting transport with this configuration causethe DS3 signal to switch automatically from the on-line working system to the redun-dant protect system, thereby ensuring continuous service.

The DS3 FLC module can be installed in several ADC FLC chassis. The module plugsinto either the FLC eight position mounting chassis, the FLC wall mount cabinet, or theDS3 FLC two position horizontal mounting chassis. Each chassis has the flexibility forvarious configurations. The eight position chassis allows up to four protected systems orfour non-protected systems. The four position wall mount cabinet can be configured forup to two protected systems or two non-protected system. The two position horizontalchassis offers up to one protected system or one non-protected system.

Description

CENTRAL OFFICE

8 POSITION UNIVERSAL

HORIZONTAL MOUNTING SHELF

SCHOOL #3

SCHOOL #1 SCHOOL #2

DS3

FLC

W

DS3

FLC

W

3/3

SWITCH

VIDEOCODEC

OPTICAL

BUDGET

= 13 dB

OPTICAL

BUDGET

= 13 dB

FOUR POSITION

UNIVERSAL

WALL MOUNTD

S3

FL

C

W

D

S3

FL

C

P

OPTICAL

BUDGET

= 13 dB

DS

3F

LC

W

VIDEO

CODEC

T1

MULTIPLEXER

TWO POSITION

RACK MOUNT

DS3

VIDEO

SIGNAL

110V

AC

110V

AC

QFLC

W

QF

LC

W

8 POSITION UNIVERSAL

HORIZONTAL MOUNTING SHELF

T1

MULTIPLEXER

AC/DC

converter

DS3

FLC

W

DS3

FLC

P

VIDEOCODEC

D

S3

FL

C

W

Q

FL

C

W

QFL

C

W

Figure 1

8/2/2019 1211_3594

3/43

DS3 FLC Distance Learning Application Note 1211

Application Figure 1 illustrates ADC DS3 FLCs used in a typical distance learning application. Aneight position chassis occupies the central office and contains several configurations.The three DS3 FLCs in the central office allow for video transmission, with an opticalbudget of not less than 13 dB, to three remote schools with a DS3 FLC in either an eightposition chassis, a four position wall-mount cabinet or a two position chassis at theschool location.

The versatility of the fiber loop converter system allows for DS1 signal transmission inaddition to DS3 video traffic. The extra slots in the remote chassis may be occupied byother DS3 FLC modules or ADC's Quad Fiber Loop Converter (QFLC) which provides foroptical transmission of DS1 voice and data signals. Several combinations of signaltransmission exist.

The four position wall-mount cabinet has a redundant AC/DC power converter whichconverts 110V AC power from a standard wall outlet to the necessary -48 V DC. Thisoption saves the expense of buying a rectifier.

Advantages ADCs DS3 FLC offers definite advantages over other DS3 transport systems. The DS3FLC provides an alternative to OC-3 multiplexers, allowing an economical last mile DS3transport or point-of-presence hand-off. Configuration options permit the system tomaximize facilities utilized for point-to-point or point-to-multipoint network topologies.The DS3 FLC requires no common equipment to operate because it integrates allfunctions onto a single printed circuit board. This feature reduces both start-up andspare inventory costs. Compared to OC-3 multiplexers, the DS3 FLC offers greatercapacity for transporting a clear channel DS3. Up to four protected systems can behubbed out of one rack mount chassis versus three DS3 systems by an OC-3 Mux.

The DS3 FLC is a plug, play, and walk away system. No need exists for hand-held termi-

nals or craft interface access for turn-up of service. Installer training is minimal and canbe provided either by ADC or your in-house training department using ADC coursematerial. The same DS3 FLC module is interchangeable for the central office terminaland the remote terminal, for either main or protect channels. One module fits alllocations and applications, thereby keeping spare inventory costs to a minimum. Eachmodule is a fully integrated system, simplifying trouble-shooting when needed.

At the remote end, the FLC customer premises wall mount chassis is perfect for handingoff DS3 and DS1 hicaps to end users. Installed in two of the customer premises chassisfour slots, the QFLC can be used to deliver four protected DS1 hicap circuits; DS3 FLCscan be installed in the other two slots to deliver one protected DS3 hicap. Or, all fourslots can be dedicated to DS3 FLCs to provide two protected DS3 hicap circuits.

8/2/2019 1211_3594

4/4

Application Note 1211 11/94 Original 1994 ADC Telecommunications, Inc. All Rights Reserved An Equal Opportunity Employer

Specifications published here are current as of the date of publication of this document. Because we are continuously improving our products,ADC reserves the right to change specifications without prior notice. At any time, you may verify product specifications by contacting our

headquarters office in Minneapolis.

ADCTelecommunications, Inc.4900 West 78th StreetMinneapolis, Minnesota 55435FAX: (612) 946-3292

For U.S. Sales, Call Toll Free: 1-800-366-3891

Telecommunications

International Sales Offices: Belgium 32-2-721-5282 United Kingdom44-734-441955 Montreal, Quebec (514) 677-9166 Vancouver, BC(604) 270-1675 Toronto, Ont. (905) 629-3104 Ottawa, Ont. (613)596-9937 Singapore 65-225-8228 Venezuela 58-2-953-1684 Mexico City, Mexico 525-658-4519 Sydney, Australia 61-2-975-1499