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Wavelength Division Multiplexing (WDM) Laser Vibrometer

Signal Conditioning and Processing

Fritz BekkadalCEO

Gersemia

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Initial (Mach–Zehnder) configuration for a single-channel setup

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Demodulation and signal conditioning

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To DSP/PC Demodulator

Baseband conditioning

and ADC

Driver (fB)

Φ

Coherent homodyne approach

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Quadrature demodulator

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Baseband conditioning and ADC

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• The gain adjustments of the I and Q channel amplifiers should be coupled, and preferably be performed electronically. • Initial estimations indicate a gain in the order of 10-20 dB.

fS

A D

Decimation

Analog anti-aliasing LP filter

Amplifier (with adjustable gain)

Digital LP filter

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ADC Front-end circuit

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ADC Front-end design

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BW ≥ 10 MHz

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ADC

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Signal-to-Noise Ratio (SNR)

As a ’rule-of-thumb’: at least an 8 bit ADC is required

…but due to the ADC Dynamic Range (DR) requirements at least a 12 bit ADC is recommended !

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A Q

A Q

SSNR

N NSNR SNR

10Q ASNR SNR

6QSNR dB b

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ADC Dynamic Range (DR)

DRQ > 60 dB is jugded a minimum with signal compression?

at least a 12 bit ADC is required

Signal compression: Large DC and reflections in the collimator’s vicinity to be

suppressed?

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6( 1)QDR dB b

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Example of ADC saturation

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