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US 7,609,982 B2Granted
RZ-DPSK optical receiver circuit
AssigneeFujitsu Limited
InventorTadashi Ikeuchi
Life of this patent
Estimating the term…
Abstract
A received RZ-DPSK signal is guided to an interferometer. The interferometer comprises a 1-bit delaying element in an upper arm. A balanced photodiode converts a pair of optical signals output from the interferometer into electrical signal. A high-pass filter, which has a cut-off frequency equal or approximately equal to the symbol rate of transmission data, filters the signal output from the balanced photodiode. A BPSK demodulator circuit demodulates the output signal of the high-pass filter.
Claims10
A RZ-DPSK optical receiver circuit comprising:
- an interferometer, comprising a 1-symbol delaying element in one of paired optical paths, for transmitting an input RZ-DPSK signal via the paired optical paths;
- a photo detector circuit for converting an optical signal output from said interferometer into an electrical signal;
- a high-pass filter with a cut-off frequency which is equal or approximately equal to the symbol rate of the RZ-DPSK signal, for filtering an output signal of said photo detector circuit;
- and
- a BPSK demodulator circuit for demodulating an output signal of said high-pass filter, wherein
- said interferometer outputs a pair of complementary optical signals, and
- said photo detector circuit comprises a pair of photodiodes for respectively converting the pair of the optical signals into a pair of electrical signals and outputs a differential signal of the pair of electrical signals acquired by the pair of photodiodes, and
- said high-pass filter acquires a BPSK signal from the differential signal, and
- said BPSK demodulator circuit demodulates the BPSK signal.
6 more elements
A RZ-DPSK optical receiver circuit, comprising:
- an interferometer, comprising a 1-symbol delaying element in one of paired optical paths, for transmitting an input RZ-DPSK signal via the paired optical paths;
- a photo detector circuit for converting an optical signal output from said interferometer into an electrical signal;
- removing means for removing frequency component lower than the symbol rate of the RZ-DPSK optical signal from the output signal of said photo detector circuit;
- and
- a BPSK demodulator circuit for demodulating the signal, whose frequency component lower than the symbol rate being removed by said removing means, wherein
- said interferometer outputs a pair of complementary optical signals, and
- said photo detector circuit comprises a pair of photodiodes for respectively converting the pair of the optical signals into a pair of electrical signals and outputs a differential signal of the pair of electrical signals acquired by the pair of photodiodes, and
- said removing means acquires a BPSK signal from the differential signal, and
- said BPSK demodulator circuit demodulates the BPSK signal.
6 more elements
A RZ-DQPSK optical receiver circuit, comprising:
- an optical splitter for generating first and second RZ-DQPSK signals by splitting a RZ-DQPSK signal;
- a first interferometer, comprising a 1-symbol delaying element in one of a pair of optical paths and a phase shifter for shifting the phase of a carrier wave of the first RZ-DQPSK signal by π/4 in the other optical path of the pair, for transmitting the first RZ-DQPSK signal via the pair of the optical paths;
- a first photo detector circuit for converting an optical signal output from said first interferometer into an electrical signal;
- a first high-pass filter with a cut-off frequency which is equal or approximately equal to the symbol rate of the RZ-DQPSK optical signal, for filtering the output signal of said first photo detector circuit;
- a first BPSK demodulator circuit for demodulating the output signal of said first high-pass filter;
- a second interferometer, comprising a 1-symbol delaying element in one of a pair of optical paths and a phase shifter for shifting the phase of a carrier wave of the first RZ-DQPSK signal by −π/4 in the other optical path of the pair, for transmitting the second RZ-DQPSK signal via the pair of the optical paths;
- a second photo detector circuit for converting an optical signal output from said second interferometer into an electrical signal;
- a second high-pass filter with a cut-off frequency which is equal or approximately equal to the symbol rate of the RZ-DQPSK optical signal, for filtering the output signal of said second photo detector circuit;
- a second BPSK demodulator circuit for demodulating the output signal of said second high-pass filter;
- and
- a signal processing circuit for regenerating data stream from the output of said first and second BPSK demodulator circuits, wherein
- said first interferometer outputs a pair of complementary optical signals, and
- said first photo detector circuit comprises a pair of photodiodes for respectively converting the pair of the optical signals into a pair of electrical signals and outputs a first differential signal of the pair of electrical signals acquired by the pair of photodiodes, and
- said first high-pass filter acquires a first BPSK signal from the first differential signal, and
- said first BPSK demodulator circuit demodulates the first BPSK signal, and
- said second interferometer outputs a pair of complementary optical signals, and
- said second photo detector circuit comprises a pair of photodiodes for respectively converting the pair of the optical signals into a pair of electrical signals and outputs a second differential signal of the pair of electrical signals acquired by the pair of photodiodes, and
- said second high-pass filter acquires a second BPSK signal from the second differential signal, and
- said second BPSK demodulator circuit demodulates the second BPSK signal.
16 more elements
Dependencies are inferred from the claim text.