Patent ID: 7444084
Filing Date: 2008-10-28
Classification: H04B

Abstract:
1. An optical signal receiver for receiving and frequency-demodulating an optical signal, comprising: an optical branch circuit for splitting an input optical signal into a first optical signal and a second optical signal; an optical delay line for delaying the first optical signal; a first photoelectric conversion circuit for converting the optical signal from the optical delay line into a first electrical signal; a second photoelectric conversion circuit for converting the second optical signal into a second electrical signal; a rectangular-wave forming means that outputs a single rectangular-wave signal using the first electrical signal from the first photoelectric conversion circuit and the second electrical signal from the second photoelectric conversion circuit as inputs; and a smoothing circuit for smoothing the rectangular-wave signal from the rectangular-wave forming means, wherein the rectangular-wave forming means comprises: a first limiter amplifier that limits and amplifies the first electrical signal from the first photoelectric conversion circuit and outputs a first binary signal; a second limiter amplifier that limits and amplifies the second electrical signal from the second photoelectric conversion circuit and outputs a second binary signal; an adder circuit that adds the first binary signal from the first limiter amplifier and the second binary signal of the second limiter amplifier and outputs a ternary signal; and a high level discriminator that discriminates the level of the ternary signal from the adder circuit by comparing its magnitude with a threshold existing between a level when the optical signal is inputted into both the first photoelectric conversion circuit and the second photoelectric conversion circuit and a level when the optical signal is inputted into either the first photoelectric conversion circuit or the second photoelectric conversion circuit and outputs the single rectangular-wave signal.