DEVICE AND METHOD FOR MONITORING OPTICAL SIGNAL QUALITY, AND OPTICAL TRANSMISSION DEVICE

• US 20150155934A1
• Filed: 11/10/2014
• Published: 06/04/2015
• Est. Priority Date: 11/29/2013
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakagawa, Goji, Aoki, Yasuhiko
• Granted Patent: US 9,496,953 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 10/0775 Performance monitoring and measurement of transmission parameters
• CPC Class Codes: H04B 10/0795 Performance monitoring; Measurement of transmission parameters
• CPC Class Codes: H04B 2210/074 using a superposed, over-modulated signal

Abstract

A device for monitoring optical signal includes: an optical filter configured to allow part of a spectrum of an optical signal on which a frequency or phase modulated signal is superimposed to pass; and a detection unit configured to detect signal quality of the optical signal, based on a power ratio of a signal component to a noise component of the modulated signal, the power ratio being obtained based on a power change in accordance with the modulated signal of light that has been caused to pass through the optical filter.

Claims

1. A device for monitoring optical signal, comprising:

an optical filter configured to allow part of a spectrum of an optical signal on which a frequency or phase modulated signal is superimposed to pass; and

a detection unit configured to detect signal quality of the optical signal, based on a power ratio of a signal component to a noise component of the modulated signal, the power ratio being obtained based on a power change in accordance with the modulated signal of light that has been caused to pass through the optical filter.

2. The device according to claim 1, wherein the optical filter has a central wavelength at a wavelength shifted with respect to a center wavelength of the spectrum.

3. The device according to claim 1, wherein the modulated signal is a signal modulated by a sinusoidal signal.

4. The device according to claim 1, wherein the detection unit comprises

an optical detector configured to receive light that has been caused to pass through the optical filter, and to output an electrical signal in accordance with power of the received light,

a Fourier transformer configured to perform a Fourier transform on the electrical signal,

a storage unit configured to store data representing a relationship of the power ratio and the signal quality, and

an operation unit configured to calculate the power ratio from a result of a Fourier transform performed by the Fourier transformer, and to acquire signal quality for the calculated power ratio from the data stored in the storage unit.

5. The device according to claim 1, wherein a first modulated signal and a second modulated signal are superimposed on the optical signal, and a frequency deviation of the first modulated signal differs from a frequency deviation of the second modulated signal.

6. The device according to claim 5, wherein one of the first and second modulated signals is a signal modulated by a sinusoidal signal, and a frequency deviation of the one of the modulated signals is smaller than a frequency deviation of the other of the modulated signals.

7. The device according to claim 6, wherein the frequency deviation of the one of the modulated signals is set in a range in which the power ratio obtained for the one of the modulated signals is lower than the power ratio obtained for the other of the modulated signals, and in which a change in the signal quality for a change in the power ratio is larger in the one of the modulated signals than in the other of the modulated signals.

8. The device according to claim 7, wherein the range is a range in which the power ratio obtained for the one of the modulated signals falls from 8 dB to 12 dB.

9. The device according to claim 6, wherein the other of the modulated signals includes one or both of information identifying an optical path and information on an optical transmitter that has transmitted the optical signal.

10. The device according to claim 1,

wherein the optical signal is a wavelength-division multiplexed signal including optical signals of a plurality of wavelengths, and

wherein the modulated signal is superimposed on an optical signal of a wavelength that is not adjacent to a wavelength of the modulated signal.

11. The device according to of claim 1,

wherein the optical filter is a tunable filter capable of changing a central wavelength, and

wherein the optical signal quality monitoring device further comprises a filter control unit configured to perform a sweep of the central wavelength of the tunable filter, and to set the central wavelength at a wavelength at which power of the signal component of the modulated signal is maximized in accordance with the sweep.

12. The device according to claim 11,

wherein the optical signal is a wavelength-division multiplexed signal including optical signals of a plurality of wavelengths, and

wherein the tunable filter is shared with an optical channel monitor configured to sweep the central wavelength and to detect power of the optical signals of the plurality of wavelengths.

13. A method for monitoring optical signal, comprising:

allowing part of a spectrum of an optical signal on which a frequency or phase modulated signal is superimposed to pass, by using an optical filter; and

detecting signal quality of the optical signal, based on a power ratio of a signal component to a noise component of the modulated signal, the power ratio being obtained based on a power change in accordance with the modulated signal of light that has been caused to pass through the optical filter.