Abstract: A phase-shift keyed signal demodulator is disclosed including a filter positioned to receive an input beam, a first photodiode positioned to receive light reflected from the filter, and a second photodiode positioned to receive light transmitted through the filter. A difference between outputs of the first and second photodiodes is interpreted to determine a data value encoded in the input beam. In another embodiment N filters receive inputs from a splitter and include transmission functions offset from one another. N pairs of photo diodes receive the transmitted and reflected beams from each filter and a decoder converts the outputs of the pairs of photodiodes to one or more data symbols.

Abstract: In an embodiment of the invention the circuit for monitoring an optical signal detector comprises a current divider current mirror and a current multiplier current mirror. The current divider current mirror has a mirror leg and a primary leg. The primary leg is coupled to the optical signal detector. The current divider current mirror is configured to generate mirror leg current corresponding with a fraction of the primary leg current. The current multiplier current mirror has a mirror leg and a primary leg coupled to the mirror leg of the current divider current mirror. The current multiplier current mirror is configured to generate mirror leg current corresponding with a multiple of the primary leg current. In another embodiment the circuit comprises a first and second current mirror.