DC to 12-GHz Photoreceivers
Appendix III: Inside the Photoreceiver • 19
Appendix III:
Inside the Photoreceiver
A gold-plated microwave housing inside the
photoreceiver module contains the high-frequency
circuitry. This housing is bolted to a printed-circuit
board which regulates the bias for the photodiode and
amplifies the DC photocurrent for the monitor port.
The optical signal is brought from the front-panel
connector to the microwave housing with a single-
mode (SM) 9-µm core fiber (Models 1544-B and 1554-B),
a multimode (MM) 62.5-µm core fiber (Model 1580-B),
or a multimode 50-µm core fiber (-50 models).
Although the material and modal dispersion per unit
length of this fiber can be high at certain wavelengths,
there is no degradation in frequency response since
the fiber is only 0.1 meters long. The “-50” versions use
a 50/125-µm fiber and a lens to image the core onto the
detector active area.
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