OPTICAL RECEIVER AND OPTICAL RECEIVING METHOD

• US 20100098411A1
• Filed: 10/16/2009
• Published: 04/22/2010
• Est. Priority Date: 10/17/2008
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: NAKASHIMA, Hisao, Tanimura, Takahito
• Granted Patent: US 8,532,503 B2
• Time in Patent Office: Days
• US Class Current: 398/25
• CPC Class Codes: H04B 10/60 Receivers
• CPC Class Codes: H04B 10/614 comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers H04J14/06 takes precedence
• CPC Class Codes: H04B 10/65 Intradyne, i.e. coherent receivers with a free running local oscillator having a frequency close but not phase-locked to the carrier signal

Abstract

An optical receiver includes a photo-detector that converts a received optical signal into an electric signal and outputs the electric signal, a converter that converts the electric signal into a parallel data signal and outputs the parallel data signal, and parallel-number changer changing a parallel number of the parallel data signal in accordance with a bit rate of the optical signal and outputting the parallel data signal having the changed parallel number.

Claims

1. An optical receiver, comprising:

a photo-detector that converts a received optical signal into an electric signal and outputs the electric signal;

a converter that converts the electric signal into a parallel data signal and outputs the parallel data signal; and

parallel-number changer changing a parallel number of the parallel data signal in accordance with a bit rate of the optical signal and outputting the parallel data signal having the changed parallel number.

2. The optical receiver according to claim 1, wherein the parallel-number changer includes a changing portion that outputs the parallel data signal having the changed parallel number and a non-changing portion that does not change the parallel number of the parallel data signal output from the converter, and

wherein the changing portion receives the parallel data signal output from the converter when the bit rate of the optical signal corresponds to a first bit rate, and the non-changing portion receives the parallel data signal output from the converter when the bit rate of the optical signal corresponds to a second bit rate.

3. The optical receiver according to claim 1, wherein the parallel-number changer includes a plurality of changing means for outputting parallel data signals having different parallel numbers from each other in correspondence to a plurality of bit rates, and selectively uses, among the plurality of changing means, changing means that corresponds to the bit rate of the optical signal.

4. The optical receiver according to claim 3, wherein each of the plurality of changing means changes a sampling rate of the parallel data signal output from the converter so as to change the parallel number of the parallel data signal.

5. The optical receiver according to claim 4, wherein each of the plurality of changing means includes upsampling means for increasing the sampling rate of the parallel data signal output from the converter, averaging filter means for averaging a data signal output from the upsampling means and outputting the data signal, and downsampling means for decreasing the sampling rate of the data signal output from the averaging filter means.

6. The optical receiver according to claim 1, further comprising acquiring means for acquiring bit rate information about the optical signal and outputting the bit rate information to the parallel-number changer.

7. The optical receiver according to claim 6, wherein the acquiring means acquires the bit rate information from a network control device.

8. The optical receiver according to claim 6, wherein the acquiring means acquires the bit rate information based on an amount of change per unit time of a sampling phase of the parallel data signal output from the converter or the parallel data signal having the changed parallel number and the frequency of a sampling clock signal used by the converter.

9. The optical receiver according to claim 6, wherein the acquiring means acquires the bit rate information based on a spectrum shape of an optical spectrum of the optical signal.

10. The optical receiver according to claim 1, wherein the converter includes anti-aliasing filter means having a filter band that changes in accordance with the bit rate of the optical signal and filters the electric signal.

11. The optical receiver according to claim 1, wherein the optical receiver further comprises:

converting means for converting an electric signal detected from a received optical signal into a parallel data signal and outputting the parallel data signal, wherein

the parallel-number changer changes the parallel number of the parallel data signal in accordance with the bit rate of the optical signal and outputs the parallel data signal having the changed parallel number.

13. An optical communication system including a polarization-multiplexing optical transmitter that modulates two orthogonal polarized-wave components using different pieces of signal information and transmits the polarized-wave components, and the optical receiver according to claim 1,

wherein, if characteristics of a received signal do not satisfy predetermined characteristics, the optical communication system performs communication using only one polarized wave.

14. The optical communication system according to claim 13, wherein the optical communication system has redundancy such that, when the bit rate of the optical signal is decreased, one polarization channel serves as a primary line and another polarization channel serves as a secondary line.

15. An optical communication system including a multicarrier optical transmitter that modulates a plurality of subcarriers using different pieces of signal information and transmits the subcarriers, and the optical receiver according to claim 1,

wherein, if characteristics of a received signal do not satisfy predetermined characteristics, the optical communication system performs communication after decreasing the number of carriers to be transmitted.

16. The optical communication system according to claim 13, wherein the optical communication system includes a multilevel optical transmitter that performs transmission after modulating multilevel information in one symbol time,

wherein, if the characteristics of the received signal do not satisfy the predetermined characteristics, the optical communication system performs communication after reducing a multilevel value.

12. An optical receiving method, comprising:

converting an optical signal into an electric signal;

converting the electric signal into a parallel data signal; and

changing a parallel number of the parallel data signal in accordance with a bit rate of the optical signal.

17. An optical communication system, comprising:

an optical receiver that includes;

a photo-detector that converts a received optical signal into an electric signal and outputs the electric signal,

a converter that quantizes the electric signal, converts the electric signal into a parallel data signal, and outputs the parallel data signal,

parallel-number changer changing a parallel number of the parallel data signal in accordance with a bit rate of the optical signal and outputting the parallel data signal having the changed parallel number,

a signal processor that demodulates a received signal based on the parallel data signal,

a monitor that monitors the quality of the demodulated signal, and

a communication device that informs a transmitter that the signal quality is equal to or below a predetermined value; and

an optical transmitter including a bit-rate changing device that changes the bit rate based on the informed signal quality.

18. The optical communication system according to claim 17, wherein the optical communication system further comprises a bidirectional communication system, wherein, when the quality of a received signal does not satisfy the predetermined value, the optical communication system changes the bit rate of an opposing transmitter and informs the transmitter of the quality.