20 • Appendix II: Inside the Photodetector
NEW FOCUS, Inc.
Appendix II:
Inside the Photodetector
A gold-plated microwave housing inside the
photodetector 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 9-cm fiber.
The fiber is protected by a sheet metal flange to prevent
damage while changing the battery. A simplified
schematic is provided below.
Figure 3:
Simplified
schematic of
the Models
1480 & 1481
photodetector
modules
–
+
–
+
V
+
V
-
V
+
V
-
V
-
V
+
V
-
Microwave
Housing
Photodiode
Microwave
Output
Connector
On/Off
Batt
Chk
Bias
Monitor
1480 FC Det revA.fm Page 20 Monday, March 13, 2000 2:55 PM
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