WO2004068093A1

WO2004068093A1 - Method for detecting wavelength and circuit for detecting wavelength and apparatus employing them

Info

Publication number: WO2004068093A1
Application number: PCT/JP2003/000921
Authority: WO
Inventors: Kensuke Matsui; Akihiko Hayashi; Norio Nagase; Kakuji Inoue; Hiroshi Yamada
Original assignee: Fujitsu Limited
Priority date: 2003-01-30
Filing date: 2003-01-30
Publication date: 2004-08-12

Abstract

An apparatus arranged to multiplex an optical signal obtained by modulating a reference light having a periodically varying wavelength with specified pattern data and an optical signal being detected before converting them into an electrical signal, to detect the error rate of the electrical signal with respect to the specified pattern data, and to detect the wavelength components included in the optical signal being detected from the wavelength of the reference light at such a timing as the error rate exceeds a specified value. With such an arrangement, a plurality of wavelengths included in the optical signal being detected can be detected collectively and optical components including prisms can be omitted while reducing the size and the cost.

Description

Description: Wavelength detection method, wavelength detection circuit, and apparatus using the same

The present invention relates to a wavelength detection method, a wavelength detection circuit, and an apparatus using the same, and more particularly, to a wavelength detection method, a wavelength detection circuit, and an apparatus using the same for detecting a wavelength component propagating in a WDM optical communication system. About. Background art

Optical communication systems are evolving into systems in which the optical processing domain called the photonic network is expanded to the conventional electrical domain, and one of the technologies supporting this is wavelength division multiplexing (WDM) optical communication.

In a WDM optical communication system, it is necessary to arrange and maintain a high density of optical signals to be propagated. Conventionally, to realize this, the wavelength is detected using an optical spectrum analyzer, and the system is controlled.

An optical spectrum analyzer monitors an electric power level by scanning an optical filter, and has a problem that an optical component such as a prism is required, so that a mounting area is increased and a cost is increased. . Disclosure of the invention

The present invention can detect a plurality of wavelengths included in an optical signal to be detected collectively, can omit optical components such as a prism, and can reduce the size and cost. And a wavelength detection circuit and a device using the same.

In order to achieve this object, the wavelength detection method of the present invention converts an optical signal obtained by modulating a periodically changing reference light with predetermined pattern data to an optical signal to be detected, and then converts it into an electric signal. Detecting an error rate of the electrical signal with respect to the predetermined pattern data, and determining an error rate from the wavelength of the reference light at a timing when the error rate exceeds a predetermined value. It is configured to detect a wavelength component included in the detected optical signal.

According to such a wavelength detection method, a plurality of wavelengths included in the optical signal to be detected can be detected at a time, optical components such as a prism can be omitted, and miniaturization and cost reduction can be achieved. It becomes. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a first embodiment of an optical receiver using the wavelength detection circuit of the present invention.

FIG. 2 is a block diagram showing the wavelength detection circuit of FIG. 1 in more detail.

FIG. 3 is a signal waveform diagram for explaining the present invention.

FIG. 4 is a block diagram showing a circuit configuration for stabilizing the center wavelength.

FIG. 5 is a signal waveform diagram for explaining the present invention.

FIG. 6 is a block diagram of a second embodiment of the optical receiver using the wavelength detection circuit of the present invention.

FIG. 7 is a block diagram of a first embodiment of an optical transmission device using the wavelength detection circuit of the present invention.

FIG. 8 is a block diagram of a second embodiment of the optical transmission device using the wavelength detection circuit of the present invention.

FIG. 9 is a block diagram of a third embodiment of an optical transmission device using the wavelength detection circuit of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of an optical receiver using the wavelength detection circuit of the present invention. FIG. 2 is a block diagram showing the wavelength detection circuit 16 of FIG. 1 in further detail. In FIG. 1 and FIG. 2, the WDM signal propagated through the path is supplied to a branching unit 10 composed of an optical power plug or the like, where it is branched into two. One WDM signal output from the branching unit 10 is separated into each wavelength (for example, wavelength; I1 to I5) by an optical separation unit (optical DEMUX), and the optical signal of each wavelength is received by the reception unit 14. And is converted into an electric signal and output. The other WDM signal output from the branch unit 10 is supplied to the mixing unit 22 in the wavelength detection circuit 16.

On the other hand, the processing section 24 in the wavelength detection circuit 16 supplies the digital V control signal to the DZA section 26, and performs digital / analog conversion in the DZA section 26, thereby obtaining the sawtooth shown in FIG. A control signal having a wave shape is generated and supplied to the reference light source 28. As a result, the reference light source 28 outputs the reference light whose center wavelength λ 0 changes (scans) at a constant period as shown by the solid line Ia in FIG. I do.

Further, the processing unit 24 reads out the random data for error detection stored in the memory 32 and supplies it to the modulation unit 30. The modulation unit 30 modulates the reference light with the random data. Then, a scanning modulated light is generated and supplied to the mixing unit 22. In the mixing unit 22, the WDM signal and the scan modulation light are combined and supplied to the photoelectric conversion unit 34, and the converted electric signal is supplied to the processing unit 24.

The processing unit 24 monitors the error rate by comparing the electric signal supplied from the photoelectric conversion unit 34 with random data supplied from the memory 32 to the modulation unit 30. At this time, the center wavelength output from the reference light source 28; since I0 changes periodically, the WDM signal has a wavelength component as shown in FIG. 3 (Β); LX (λχ = λ1, λ 2, λ 3, λ 4), the center wavelength; I 0 is a wavelength component; at the timing overlapping with LX, beat noise due to the mixing of optical signals occurs, and the error rate sharply increases. When the error rate exceeds the threshold, the processing unit 24 performs error detection as shown in FIG. 3 (C).

Therefore, by storing the center wavelength 0 output from the reference light source 28 corresponding to the digital control signal in the memory 32 composed of an EEPROM, etc., the wavelength included in the WDM signal can be detected from the error detection timing. It is possible to collectively detect the wavelength components of the WDM signal propagating on the main line.

The processing unit 24 supplies the detected wavelength information to the control unit 18. The control unit 18 turns on only the photoelectric conversion unit corresponding to the detected wavelength among the photoelectric conversion units (Ο / Ε) 15 1 to 15 η of each wavelength constituting the reception unit 14, and The control is performed to turn off the other photoelectric conversion units for which is not detected. The control unit 18 may control the center wavelength of the optical filter corresponding to the detected wavelength among the optical filters 13 1 to 13 η constituting the light separating unit 12. In this way, detection of a plurality of wavelengths of a WDM signal can be performed collectively, and no optical components are required for wavelength detection, so that downsizing and cost reduction can be achieved.

By the way, when a VCSEL laser (surface emitting laser) capable of controlling the center wavelength λ 0 is used as the reference light source 28, the center wavelength λ 0 changes as the environmental temperature changes over time. Therefore, it is necessary to stabilize in some way because it may cause an error in the detection result.

The center wavelength λ0 can be stabilized by using a Peltier element to stabilize the laser element temperature, or by passing a part of the reference light source through an optical filter for wavelength detection and using a photodiode (PD). Although there is a method of keeping the level converted to electricity constant, in the present invention, it is realized by the configuration shown in FIG.

In FIG. 4, for example, the processing unit 24 supplies the digital control signal (initial value) read from the memory 32 to the DZA unit 26 at every jf fixed time, for example, and the control signal output from the D / A unit 26 However, as shown in FIG. 5A, control is performed so that the center wavelength of the reference light is fixed to, for example, the wavelength; La for at least a fixed time (monitoring period).

Then, a part (wavelength; La) of the reference light passing through the optical filter 36 is photoelectrically converted by a photodiode (PD) 38 and analog / digital converted by an A / D unit 40. Supply 4

The processing unit 24 compares the output level of the photodiode 38 shown in FIG. 5A with the level at the time of setting of the memory 32 during the monitoring period, and outputs the digital control signal so as to maintain the level at the time of setting. The correction is performed and the correction data is stored in the memory 32. Thereafter, the digital control signal for generating the control signal having the sawtooth waveform is corrected using this correction data.

FIG. 6 is a block diagram of a second embodiment of the optical receiver using the wavelength detection circuit of the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. In Fig. 6, the WDM signal propagated through the main line is separated into each wavelength (for example, wavelengths 1 to L5) by an optical demultiplexer (optical D EMUX). The signal is supplied to the receiving section 14 through 4 2 _ 5, converted into an electric signal, and output.

The branch / detection units 42-1-42-5 have the same configuration, of which the branch-detection unit 42-5 is illustrated in detail. Branch ・ Detection part 4 2-5, light of wavelength 5 The signal component is supplied to a branching unit 10 composed of an optical power blur or the like, where it is branched into two. One optical signal output from the branching unit 10 is supplied to the receiving unit 14, and the other optical signal is supplied to the mixing unit 22 in the wavelength detection circuit 16. As described with reference to FIG. 2, the wavelength detection circuit 16 periodically changes the central wavelength of the reference light; L0, and is supplied from the branching unit 42 based on the error rate caused by beat noise. Five wavelength components are detected from the optical signal, and the detection result is supplied to the control unit 18. The same operation is performed for the other branch / detection sections 42-1 to 42-4. The control unit 18 controls the center wavelength of each of the wavelengths I 1 to L 5 in the receiving unit 14 using the detection result.

FIG. 7 is a block diagram of a first embodiment of an optical transmission device using the wavelength detection circuit of the present invention. In the figure, a transmission unit 50 is supplied with a plurality of series of electric signals, converts each signal into an optical signal of a different wavelength (for example, wavelength; L1 to L5), and then uses an optical filter for each wavelength. The wavelength is controlled and supplied to the optical multiplexing unit (optical MUX) 52. The optical multiplexing unit 52 supplies a WDM signal obtained by multiplexing these wavelengths to the branching unit 54. A branching unit 54 composed of an optical power blur or the like splits the WDM signal into two, sends one to the main line, and supplies the other to the wavelength detection circuit 56.

The wavelength detection circuit 56 has the same configuration as the wavelength detection circuit 16 shown in FIG. 2, and as described above, the center wavelength of the reference light; 10 is periodically changed to cause the beat noise. The wavelength included in the WDM signal is detected from the error rate to be detected, and the detection result is supplied to the control unit 58. The control unit 58 controls the center wavelength of each of the wavelengths I 1 to λ 5 in the transmission unit 50 using the detection result.

FIG. 8 is a block diagram of a second embodiment of the optical transmission device using the wavelength detection circuit of the present invention. In the figure, the same parts as those in FIG. 7 are denoted by the same reference numerals. In FIG. 8, a transmission unit 50 is supplied with a plurality of series of electric signals, converts each signal into an optical signal having a different wavelength (for example, wavelength λΐ to 15), and then performs wavelength control for each wavelength to output. The optical signal of each wavelength is supplied to an optical multiplexing unit (optical MUX) 62 through a branching / detecting unit 60-1 to 60_5. The optical multiplexing unit 62 multiplexes the optical signal of each wavelength supplied from the transmission unit 50 into a WDM signal supplied from the outside, and sends out the obtained WDM signal to the main line. The branch 'detectors 60-1 to 60-5 have the same configuration, and the branch' detector 60-1 is illustrated in detail. At the branching detector 60-1, light of wavelength; L1 The signal component is supplied to a branching unit 54 composed of an optical power blur or the like, where it is branched into two. One optical signal output from the branching unit 54 is supplied to the optical multiplexing unit 62, and the other optical signal is supplied to the wavelength detection circuit 56. The wavelength detection circuit 56 has the same configuration as the wavelength detection circuit 16 shown in FIG. 2, and as described above, periodically changes the center wavelength λ 0 of the reference light, thereby causing an error caused by beat noise. The wavelength λ1 component is detected from the optical signal supplied from the branching unit 54 based on the rate, and the detection result is supplied to the control unit 58. The same operation is performed for the other branch detection units 60-0 to 60-5. The control section 58 controls the center wavelength of each of the wavelengths L1 to I5 in the transmission section 50 using the above detection result.

FIG. 9 is a block diagram of a third embodiment of the optical transmitter using the wavelength detection circuit of the present invention. In the figure, the same parts as those in FIG. 7 or FIG. In FIG. 9, a transmission unit 50 is supplied with a plurality of series of electric signals, converts each signal into an optical signal of a different wavelength (for example, wavelength λ 1 to 5), and then performs wavelength control with an optical filter for each wavelength. And supplies it to the optical multiplexing unit (optical MUX) 62. The optical multiplexing unit 62 multiplexes the optical signal of each wavelength supplied from the transmitting unit 50 into the WDM signal supplied from the branching unit 64, and sends out the obtained WDM signal to the main line.

The WDM signal supplied from the outside is supplied to a branching unit 64 composed of an optical power bra and the like, where it is branched into two. One WDM signal output from the branching unit 64 is supplied to the optical multiplexing unit 62 described above, and the other optical signal is supplied to the wavelength detection circuit 56.

The wavelength detection circuit 56 has the same configuration as the wavelength detection circuit 16 shown in FIG. 2, and as described above, the center wavelength of the reference light; L 0 is periodically changed to cause the beat noise. The wavelength included in the WDM signal supplied from the branch unit 64 is detected based on the error rate to be detected, and the detection result is supplied to the control unit 58. The control unit 58 controls the center wavelength using the detection result.

The processing section 24, the D / A section 26, the reference light source 28, and the modulation section 30 correspond to the scanning modulated light generating means described in the claims, and the mixing section 22 and the photoelectric conversion section 34 correspond to the mixed conversion. The processing unit 24 corresponds to the detecting means, the optical filter 36 and the photodiode 38 correspond to the level detecting means, the processing unit 24 corresponds to the correcting means, and the memory 34 corresponds to the detecting means. Corresponds to the storage method.

Claims

The scope of the claims .

1. An optical signal obtained by modulating a reference light whose wavelength periodically changes with predetermined pattern data is multiplexed with an optical signal to be detected, and then converted into an electric signal.

A wavelength detection method for detecting an error rate of the electrical signal with respect to the predetermined pattern data, and detecting a wavelength component included in the detected light signal from a wavelength of the reference light at a timing when the error rate exceeds a predetermined value.

2. Reference light whose wavelength changes periodically Scanning modulated light generating means for generating scanning modulated light modulated with predetermined pattern data;

A mixing conversion means for multiplexing the scanning modulated light with the optical signal to be detected and then converting it into an electric signal;

A wavelength detecting means for detecting an error rate of the electric signal with respect to the predetermined pattern data, and detecting a wavelength component included in the detected light signal from a wavelength of the reference light at a timing when the error rate exceeds a predetermined value. Detection circuit.

3. A splitting unit that splits a part of the WDM signal multiplexing multiple wavelengths supplied to the optical demultiplexing unit,

3. The wavelength detection circuit according to claim 2, wherein the WDM signal supplied from the branch unit is supplied as a detected light signal.

An optical receiving device comprising: a control unit that controls a receiving unit that receives each wavelength separated by the optical splitting unit according to a detection result output by the wavelength detection circuit.

4. a branching unit that branches a part of the optical signal obtained by separating the WDM signal obtained by multiplexing a plurality of wavelengths by the optical separation unit;

The wavelength detection circuit according to claim 2, wherein the optical signal having the wavelength supplied from the branch unit is supplied as the detected optical signal.

An optical receiving device having a control unit that controls a receiving unit that receives each wavelength demultiplexed by the optical demultiplexing unit according to a detection result output from the tfif self-wavelength detection circuit.

5. A splitter for splitting a part of the WDM signal obtained by multiplexing a plurality of wavelengths supplied from the transmitter by the optical multiplexing unit,

3. The wavelength detection circuit according to claim 2, wherein the WDM signal supplied from the branch unit is supplied as a detected optical signal.

An optical transmission device having a control unit for controlling the transmission unit for each wavelength according to a detection result output from the wavelength detection circuit.

6. The wavelength detecting circuit according to claim 2, wherein the branching unit branches a part of the optical signal having the wavelength supplied from the transmitting unit, and the optical signal having the wavelength supplied from the branching unit is supplied as the detected optical signal. When,

7.The wavelength detecting circuit according to claim 2, wherein the branching unit branches a part of the WDM signal obtained by multiplexing a plurality of wavelengths, and the WDM signal supplied from the branching unit is supplied as a detected optical signal.

An optical transmission device having a control unit that controls a transmission unit that outputs a plurality of wavelengths to be multiplexed on the WDM signal in accordance with a detection result output from the wavelength detection circuit.

8. In the wavelength detection circuit according to claim 2,

A wavelength detection circuit for changing the wavelength of the reference light using a control signal whose value periodically changes.

9. The wavelength detection circuit according to claim 8,

Level detection means for detecting the level of the reference light at the time when the control signal is a constant value,

A wavelength detection circuit comprising: a correction unit configured to correct the control signal so that a detection level of the reference light becomes a predetermined value.

10. The wavelength detection circuit according to claim 9,

A wavelength detection circuit comprising: initial data for setting the control signal to a constant value; and storage means for storing correction data for correcting the control signal.