JP2010217067A - Light signal monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To synchronize a sampling frequency of an A-D converter to that of an electric field absorption type optical modulator. <P>SOLUTION: A light signal monitoring device includes: a light pulse generator 2; an electric field absorption type optical modulator 3 as a light sampling gate; a bias voltage generator 4; a light receiving unit 5; an A-D converter 6; an optical coupler 7; a clock reproducer 21; and a delay unit 22. The light signal monitoring device for evaluating the waveform of a light signal Px measured in an equivalent sampling system further includes the clock reproducer 21 for extracting a clock signal Es of a sampling frequency for sampling the light signal Px measured from an electric signal fed from the light receiving unit 5. The A-D converter 6 converts an electric signal Ey to a digital signal in synchronization with a clock signal Es from the clock reproducer 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical signal monitoring device, and more particularly to an optical signal monitoring device that samples a measured optical signal using a self-excited oscillation type pulse light source.

  In order to perform high-resolution equivalent sampling, an optical signal monitoring device using a mutual absorption saturation characteristic of an electroabsorption optical modulator has been proposed (see, for example, Patent Document 1).

  FIG. 2 is a schematic configuration diagram of an optical signal monitoring apparatus using a mutual absorption saturation characteristic of a conventional electroabsorption optical modulator. The conventional optical signal monitoring apparatus uses an optical pulse generator 102 for generating a sampling optical pulse Ps having a constant period, and a light to be measured using a mutual absorption saturation characteristic between the optical signal Px to be measured and the optical pulse Ps for sampling. The electroabsorption optical modulator 3 that samples the signal Px, the bias voltage generator 4 that applies a DC bias voltage to the electroabsorption optical modulator 3, and the optical signal Py after sampling from the electroabsorption optical modulator 3 Is converted to an electric signal Ey, and an AD (Analog-to-Digital) converter 6 that converts the electric signal Ey from an analog signal to a digital signal Dy. By observing the digital signal Dy from the AD converter 6, the eye waveform of the measured optical signal Px is evaluated by an equivalent sampling method.

  The sampling frequency in the AD converter 6 needs to be synchronized with the sampling frequency in the electroabsorption optical modulator 3. Therefore, the conventional optical signal monitoring apparatus uses the optical pulse generator 102 that generates the sampling optical pulse Ps in accordance with the clock signal input from the reference signal generator 101 provided outside the optical pulse generator 102.

WO2008 / 087809 A1 JP2008-311423

Mathias Westlund, Henrik Sunnerud, Magnus Karlsson, and Peter A.M. Andrewkson, “Software-Synchronized All-Optical Sampling for Fiber Communication Systems,” IEEE Journal of Lightwave Technology. 23, no. 3, pp. 1088-1099, March 2005

  However, the optical pulse generator that generates sampling optical pulses in accordance with a clock signal input from the outside has a problem that the configuration is complicated and expensive.

  A passively mode-locked fiber laser can generate optical pulses for sampling with an inexpensive configuration. However, since the passive mode-locked fiber laser is a self-excited oscillation type device, the sampling frequency in the AD converter cannot be synchronized with the sampling frequency in the electroabsorption optical modulator in the conventional configuration.

  Therefore, an object of the present invention is to synchronize the sampling frequency of the AD converter with the sampling frequency of the electroabsorption optical modulator.

  In order to achieve the above object, the optical signal monitoring device of the present invention is provided with a clock regenerator that extracts a sampling frequency clock from an electrical signal obtained by photoelectrically converting a measured optical signal, and performs sampling and AD conversion of the electrical signal. It is characterized in that it is performed with the clock extracted by the clock regenerator.

  Specifically, the optical signal monitoring device of the present invention comprises an optical pulse generator that outputs a sampling optical pulse, an optical sampling gate that samples a measured optical signal according to the sampling optical pulse, and an optical sampling gate. A photoreceiver that converts the output optical signal into an electrical signal; and an AD (Analog-to-Digital) converter that converts the electrical signal from the photoreceiver into a digital signal. An optical signal monitoring device for evaluating a waveform of a measurement optical signal, further comprising: a clock regenerator that extracts a clock signal having a sampling frequency for sampling the optical signal to be measured from the electrical signal from the light receiver; The electric signal is synchronized with the clock signal from the clock regenerator. And converting the digital signal.

By further providing a clock regenerator, a clock having a sampling frequency at the optical sampling gate can be extracted. Thereby, the sampling frequency in the AD converter can be synchronized with the sampling frequency in the optical sampling gate.
In addition, it is possible to extract a sampling frequency clock at the optical sampling gate without using optical components. Thereby, the optical signal monitoring device of the present invention can be provided with a simple configuration.

  In the optical signal monitoring device of the present invention, the AD converter includes an electric sampling gate that samples the electric signal from the light receiver in synchronization with the clock signal, and outputs an output signal of the electric sampling gate as a digital signal. It is preferable to convert to

  In the optical signal monitoring device according to the present invention, the optical sampling gate is preferably an electroabsorption optical modulator that samples the optical signal under measurement using a mutual absorption saturation characteristic.

In the optical signal monitoring device according to the present invention, the optical pulse generator is preferably a passive mode-locked fiber laser.
According to the present invention, a sampling optical pulse can be generated with a simple configuration. Thereby, the optical signal monitoring device of the present invention can be provided with a simple configuration.

  The above inventions can be combined as much as possible.

  According to the present invention, in an optical signal monitoring apparatus that performs waveform evaluation of an optical signal to be measured by an equivalent sampling method, the sampling frequency in the AD converter can be synchronized with the sampling frequency in the electroabsorption optical modulator. As a result, it is possible to provide a high-resolution optical signal monitor device at low cost using a self-oscillation type optical pulse generator.

It is a schematic block diagram of the optical signal monitor apparatus which concerns on this embodiment. It is a schematic block diagram of the conventional optical signal monitor apparatus.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  FIG. 1 is a schematic configuration diagram of an optical signal monitoring apparatus according to the present embodiment. The optical signal monitoring apparatus according to the present embodiment includes an optical pulse generator 2, an electroabsorption optical modulator 3 as an optical sampling gate, a bias voltage generator 4, a light receiver 5, an AD converter 6, An optical coupler 7, a clock regenerator 21, and a delay unit 22 are provided.

  The optical pulse generator 2 outputs a sampling optical pulse Ps. The bias voltage generator 4 adjusts the voltage so that mutual absorption saturation occurs in the electroabsorption optical modulator 3 by the sampling optical pulse Ps, and applies the bias voltage to the electroabsorption optical modulator 3. The measured optical signal Px and the sampling optical pulse Ps are input to the electroabsorption optical modulator 3. Thus, the electroabsorption optical modulator 3 samples the measured optical signal Px using the mutual absorption saturation characteristics of the sampling optical pulse Ps and the measured optical signal Px. The electroabsorption optical modulator 3 outputs the sampled optical signal Py.

  The optical pulse generator 2 is a self-excited oscillation type light source that outputs a sampling optical pulse using a resonator. For example, an optical fiber type mode-locked fiber laser or a semiconductor type integrated mode-locked semiconductor laser. The optical pulse generator 2 is preferably a self-oscillation passive mode-locked fiber laser. Thereby, it is possible to easily generate a short-pulse sampling optical pulse Ps.

  The optical signal Py output from the electroabsorption optical modulator 3 is input to the light receiver 5. The light receiver 5 converts the optical signal Py into an electric signal Ey and outputs it. The AD converter 6 samples the electric signal Ey and then converts it into a digital signal Dy. By collecting the digital signal Dy from the AD converter 6, the eye waveform of the measured optical signal Px can be observed. Thereby, the waveform evaluation of the optical signal Px to be measured can be performed by an equivalent sampling method.

  Using the software synchronization method described in Non-Patent Document 1 and Patent Document 2, it is possible to generate an eye waveform from the digital signal Dy without strictly setting the repetition frequency of the sampling optical pulse.

  The electrical signal Ey output from the light receiver 5 includes a component of the sampling frequency f in the electroabsorption optical modulator 3. Therefore, the clock regenerator 21 extracts a clock having the sampling frequency f in the electroabsorption optical modulator 3 from the electric signal Ey from the light receiver 5, and outputs a clock signal Es having the frequency f. The delay unit 22 matches the phase of the clock signal Es output from the clock regenerator 21 so that the AD converter 6 acquires the peak of the electric signal Ey from the light receiver 5. The AD converter 6 converts the electric signal Ey into a digital signal Dy in synchronization with the clock signal Es from the clock regenerator 21. For example, the AD converter 6 includes an electric sampling gate 61 that samples the electric signal Ey from the light receiver 5 in synchronization with the clock signal Es, and an AD conversion stage that converts the output signal of the electric sampling gate 61 into a digital signal Dy. 62. Thereby, the AD converter 6 can sample the electrical signal Ey at a frequency synchronized with the sampling frequency in the electroabsorption optical modulator 3. Therefore, the self-excited oscillation type optical pulse generator 2 can be used. The delay device 22 may be a phase shifter that changes the phase of the sampling frequency f.

  The clock regenerator 21 is, for example, a clock regenerating circuit using a resonator that resonates at the sampling frequency f in the electroabsorption optical modulator 3 or a pulse comparator of the electric signal Ey and a VCO (Voltage Controlled Oscillator) with a phase comparator. Is a clock recovery circuit using a PLL (Phase-Locked Loop) that detects the phase difference of the VCO and adjusts the oscillation frequency or phase of the VCO.

  In this embodiment, as an example, the sampling optical pulse Ps is input from the rear (the output side of the electroabsorption optical modulator 3), and the optical signal Py is output from the rear of the electroabsorption optical modulator 3. As shown, the sampling optical pulse Ps may be input from the front (input side of the electroabsorption optical modulator 3), and the optical signal Py may be output from the rear of the electroabsorption optical modulator 3. .

  Further, the present invention is not limited to the optical signal monitoring device using the mutual absorption saturation characteristic of the electroabsorption optical modulator, and can be used for an optical signal monitoring device using another type of optical sampling gate.

  Since the present invention can perform high-resolution optical sampling, it can be applied to the information communication industry and various industries using light.

2, 102: Optical pulse generator 3: Electroabsorption optical modulator 4: Bias voltage generator 5: Light receiver 6: AD converter 7: Optical coupler 21: Clock regenerator 22, 103: Delay device 61 Electric sampling gate 62: AD conversion stage 101: Reference signal generator

Claims (4)

An optical pulse generator that outputs an optical pulse for sampling;
An optical sampling gate for sampling the optical signal under measurement according to the sampling optical pulse;
A light receiver that converts an optical signal output from the optical sampling gate into an electrical signal;
An AD (Analog-to-Digital) converter that converts the electrical signal from the light receiver into a digital signal;
In an optical signal monitoring device that performs waveform evaluation of the optical signal to be measured by an equivalent sampling method,
A clock regenerator for extracting a sampling frequency clock signal for sampling the measured optical signal from the electrical signal from the light receiver;
The AD converter converts the electrical signal into the digital signal in synchronization with the clock signal from the clock regenerator. The AD converter is
An electrical sampling gate that samples the electrical signal from the light receiver in synchronization with the clock signal;
2. The optical signal monitoring apparatus according to claim 1, wherein an output signal of the electrical sampling gate is converted into a digital signal.   3. The optical signal monitoring apparatus according to claim 1, wherein the optical sampling gate is an electroabsorption optical modulator that samples the optical signal to be measured using a mutual absorption saturation characteristic.   4. The optical signal monitoring apparatus according to claim 1, wherein the optical pulse generator is a passive mode-locked fiber laser.

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