JPH10148581A - Optical sampling waveform observing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sampling waveform observing device, wherein the waveform of each optical signal constituting optical wavelength multiplexing signal is accurately measured at a high resolution. SOLUTION: A non-linear optical crystal 3 generates a sum frequency light (SF light) of a signal light to be measured wherein optical signals of three wavelengths are wavelength-multiplexed and a sampling pulse light. A wavelength variable optical filter 5 allows the optical signal of specific wavelength, among the SF light, to pass. The photo-detector 6 converts the SF light selected with the wavelength variable optical filter 5 into electric signal. An electric signal processing part 7, based on the SF light, restores the to-be-measured signal light. Since the SF light is an optical pulse which is sampled according to sampling principle, even when the pulse width of the SF light is enlarged by dispersion characteristics and band area limit of the wavelength variable optical filter 5, no optical waveform of the to-be-measured signal light which is observed is affected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an optical sampling waveform observation apparatus for observing an optical waveform in an ultra-short time range which cannot be observed by a method using a photoelectric conversion element, and in particular, a wavelength-multiplexed ultra-high-speed optical signal. The present invention relates to an optical sampling waveform observation device capable of observing an image.

[0002]

2. Description of the Related Art A conventional optical sampling waveform observation apparatus is:
Sum-Freque light generation, which is a second-order nonlinear optical effect
ncy Generation: "SFG")
The cross-correlation between the signal light to be measured (angular frequency ω1) and the sampling pulse light (angular frequency ω2) having a smaller pulse width in the nonlinear optical crystal results in a sum frequency light having an angular frequency of (ω1 + ω2). (Hereinafter referred to as “SF light”) (see Japanese Patent Publication No. 6-63869).

FIG. 4 is a block diagram showing a configuration example of the above-mentioned conventional optical sampling waveform observation apparatus. As shown in this figure, in the conventional optical sampling waveform observation device,
The SF light generated in the nonlinear optical crystal 3 is photoelectrically converted by the light receiver 6, and the measured signal light is restored and displayed by the electric signal processing unit 7 and the display 8 based on the electric signal obtained by the photoelectric conversion. Was.

[0004]

By the way, using the conventional optical sampling waveform observation apparatus described above, an optical wavelength multiplexed signal (Wavelength-Division Multiplexing: hereinafter) in which a plurality of optical signals of different wavelengths are wavelength-multiplexed. "WDM
In this case, normal measurement could not be performed because optical signals of each wavelength were observed in an overlapping manner. That is, the above-described conventional device has a problem that it can measure only the signal light to be measured having a single wavelength.

[0005] Therefore, in order to measure a WDM signal using the conventional apparatus, before measurement (ie, before entering the optical multiplexer 2 in FIG. 4), an optical bandpass filter or the like is used. It is necessary to select an optical signal having a wavelength to be measured from a plurality of optical signals constituting the signal light to be measured. However, in this method, the waveform of the optical signal after passing through the optical band-pass filter changes due to the dispersion characteristics and loss characteristics of the optical band-pass filter, the band limitation of the optical pulse, and the like, so that accurate measurement cannot be expected. Was.

For reference, the above method (a method of selecting an optical signal of a specific wavelength using an optical band-pass filter or the like)
Will be described. When the optical wavelength is 1.55 μm used in optical communication, an optical signal (optical pulse) having a pulse width of 2.5 ps has an optical spectrum width of about 1 nm as an optical wavelength bandwidth. When this light pulse is incident on an optical bandpass filter having an optical wavelength bandwidth of 0.1 nm,
The optical band of the optical pulse is limited, and the pulse width of the output optical pulse is increased to 25 ps. Thus, in this method, the accuracy as an optical sampling waveform observation device is completely lost.

The present invention has been made under such a background. By individually detecting the optical waveform of each optical signal constituting a WDM signal, the optical waveform can be accurately measured with high resolution. It is a further object of the present invention to provide an optical sampling waveform observation device capable of accurately measuring not only the optical waveform but also the optical wavelength.

[0008]

According to the first aspect of the present invention,
For a signal light to be measured in which a plurality of optical signals of different wavelengths are wavelength-multiplexed, a sampling pulse light source that outputs a sampling pulse light having a wavelength different from each of the optical signals, the signal light to be measured and the sampling pulse A multiplexing means for multiplexing light and an output light of the multiplexing means, and a sum frequency light of each of the wavelength-multiplexed optical signals and the sampling pulse light corresponds to each of the optical signals. Sum frequency light generating means for outputting the sum wavelength light, the light wavelength selecting means for selecting and outputting only the sum frequency light of a specific wavelength among the sum frequency lights output by the sum frequency light generating means, Detecting means for detecting the sum frequency light output from the means, and processing means for restoring an original optical signal corresponding to the sum frequency light based on the sum frequency light detected by the detecting means. It is characterized by. According to a second aspect of the present invention, in the optical sampling waveform observation device according to the first aspect, the optical wavelength selection means changes the wavelength of the sum frequency light to be selectively output to an arbitrary value. The invention according to claim 3 is a sampling pulse light source that outputs a sampling pulse light having a wavelength different from each optical signal to a signal light to be measured in which a plurality of optical signals having different wavelengths are multiplexed, Multiplexing means for multiplexing the signal light to be measured and the sampling pulse light, and an output light from the multiplexing means, and a sum frequency light of each of the wavelength-multiplexed optical signals and the sampling pulse light. A sum frequency light generating means for outputting corresponding to each optical signal, a light wavelength diffracting means for diffracting the sum frequency light output by the sum frequency light generating means at a different angle for each light wavelength, Light receiving elements are arranged in an array, a light receiving element array for receiving each sum frequency light diffracted by the light wavelength diffracting means, and each sum frequency based on each sum frequency light detected by the light receiving element array. Original light corresponding to light Characterized by comprising a processing unit for restoring the item. According to a fourth aspect of the present invention, in the optical sampling waveform observation device according to any one of the first to third aspects, the sum frequency light generating means includes a sum frequency light generating effect element that generates the sum frequency light. And a removing means for outputting only the generated sum frequency light. The invention according to claim 5 is a sampling pulse light source that outputs a sampling pulse light having a wavelength different from each of the optical signals to a signal light to be measured in which a plurality of optical signals having different wavelengths are multiplexed; Multiplexing means for multiplexing the signal light to be measured and the sampling pulse light, and output light of the multiplexing means, and a difference frequency light between each of the wavelength-multiplexed optical signals and the sampling pulse light. A difference frequency light generating means for outputting corresponding to each optical signal, and a light wavelength for selecting and outputting only a difference frequency light of a specific wavelength among the difference frequency lights output by the difference frequency light generating means. Selecting means, detecting means for detecting the difference frequency light output from the light wavelength selecting means, and restoring an original optical signal corresponding to the difference frequency light based on the difference frequency light detected by the detecting means. Processing means And it features. According to a sixth aspect of the present invention, in the optical sampling waveform observation device according to the fifth aspect, the optical wavelength selecting means changes the wavelength of the difference frequency light to be selectively output to an arbitrary value. The invention according to claim 7 is a sampling pulse light source that outputs a sampling pulse light having a wavelength different from each of the optical signals to a signal light to be measured in which a plurality of optical signals having different wavelengths are multiplexed; Multiplexing means for multiplexing the signal light to be measured and the sampling pulse light, and output light of the multiplexing means, and a difference frequency light between each of the wavelength-multiplexed optical signals and the sampling pulse light. A difference frequency light generating means for outputting corresponding to each of the optical signals; a light wavelength diffracting means for diffracting the difference frequency light output by the difference frequency light generating means at a different angle for each light wavelength; Light receiving elements are arranged in an array, and a light receiving element array for receiving each difference frequency light diffracted by the light wavelength diffracting means, and each difference frequency light based on each difference frequency light detected by the light receiving element array. Original light corresponding to light Characterized by comprising a processing unit for restoring the item. According to an eighth aspect of the present invention, in the optical sampling waveform observation device according to any one of the fifth to seventh aspects, the difference frequency light generating means includes a difference frequency light generating effect element that generates the difference frequency light. ,
And removing means for outputting only the generated difference frequency light. According to a ninth aspect of the present invention, in the optical sampling waveform observation apparatus according to any one of the first to eighth aspects, the sampling pulse light source sets the wavelength of the sampling pulse light output from the sampling pulse light source to an arbitrary value. Is selected.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

§1. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of the optical sampling waveform observation device according to the first embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. In the optical sampling waveform observation device shown in this figure, a wavelength tunable optical filter 5 is newly provided.

In FIG. 1, the signal light to be measured is obtained by wavelength multiplexing optical signals having three wavelengths of optical angular frequencies ω1-1, ω1-2, ω1-3. The sampling pulse light source 1 generates a sampling pulse light (angular frequency ω2) having a light pulse width narrower than the signal light to be measured. Note that the sampling pulse light source 1 can select an arbitrary value for the angular frequency ω2 of the sampling pulse light. The optical multiplexer 2 multiplexes the signal light to be measured and the sampling pulse light, and makes the multiplexed light incident on the nonlinear optical crystal 3 (KTP or the like).

At this time, if the phase matching condition is satisfied by setting the crystal orientation, the environmental temperature and the like so that SFG can occur in the nonlinear optical crystal 3, the nonlinear optical crystal 3
Generates SF light. The SF light is output from the nonlinear optical crystal 3 together with the signal light to be measured and the sampling pulse light.

FIG. 2 is a graph showing the principle of SFG in this embodiment. At this time, if the nonlinear optical crystal 3 is set so as to satisfy the phase matching condition, SF light is emitted from the nonlinear optical crystal 3 only when both the signal light to be measured and the sampling pulse light are incident on the nonlinear optical crystal 3. can get. Therefore, by slightly shifting (lowering or increasing) the repetition frequency of the sampling pulse light to an integer fraction of the repetition frequency of the signal light to be measured, SF light obtained by sampling the signal light to be measured can be obtained. And in this case, according to the principle of sampling,
The waveform of the signal light to be measured can be restored from the obtained SF light.

In this embodiment, since the signal light to be measured is obtained by wavelength multiplexing optical signals of three wavelengths, optical signals of three wavelengths are generated as SF light as shown in FIG. , Respectively, ω1-1 + ω2, ω1-2 + ω2, ω1-3
It has an angular frequency of + ω2. That is, the SF light is
It has an angular frequency correlated with the angular frequency of the signal light to be measured.

Next, the fundamental wave removing filter 4 shown in FIG.
Removes the SF light, the signal light to be measured, and the sampling pulse light output from the nonlinear optical crystal 3 other than the SF light. The system up to this point is the same system as the prior art shown in FIG.

Next, the wavelength tunable optical filter 5 outputs the SF light (angular frequency ω1-1 +
ω2, ω1-2 + ω2, ω1-3 + ω2) are selected, and only an optical signal of a specific wavelength is passed. Then, the light receiver 6 detects the SF light selected by the wavelength variable optical filter 5 and converts the SF light into an electric signal. The electric signal processing unit 7 performs predetermined processing (A / D conversion, A / D converted SF) on the electric signal detected and converted by the light receiver 6.
(Restoration of the signal light to be measured based on the light). Then, the display 8 displays the restored waveform of the signal light to be measured.

In the present embodiment, since the SF light is an optical pulse sampled according to the principle of sampling, it can be selectively cut out using the wavelength tunable optical filter 5 so that even if the pulse width of the SF light is tunable. Even if it is spread due to the dispersion characteristics of the optical filter 5 and the band limitation, the optical waveform of the signal light under measurement observed as the optical sampling waveform has no influence. That is, in the present embodiment, even if wavelength selection is performed using an optical filter (wavelength tunable optical filter 5), there is no effect on the measurement time resolution and the three optical signals constituting the signal light to be measured are selected. By selectively sampling only the optical signal of a specific wavelength, the optical waveform of the optical signal of the specific wavelength can be observed.

For example, when one of the three optical signals constituting the signal light to be measured has a wavelength of 1.55 μm and the sampling pulse light has a wavelength of 1.54 μm,
An optical pulse having a wavelength of 0.77 μm is generated as the corresponding SF light. This SF light is used as a tunable optical filter 5.
When wavelength selection is performed using a narrow band optical filter having a pass band width of 0.1 nm, the wavelength range of the light to be measured is 1.5.
It corresponds to 498 μm to 1.5502 μm. Therefore,
According to this apparatus, optical sampling can be performed with a wavelength resolution of 0.4 nm. The measurement time resolution is
Since it is determined only by the pulse width of the sampling pulse light, a time resolution of about 100 fs can be obtained without any problem.

In this embodiment, when a narrow band optical filter is used as the wavelength variable optical filter 5, not only the optical pulse waveform but also the optical wavelength distribution can be measured. In this case, by sweeping the transmission center wavelength of the tunable optical filter 5, the waveform of the signal light to be measured can be displayed three-dimensionally using the time axis, the wavelength axis, and the light intensity axis.

§2. Second Embodiment Next, a second embodiment of the present invention will be described. FIG.
FIG. 6 is a block diagram illustrating a configuration example of an optical sampling waveform observation device according to a second embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the optical sampling waveform observation device shown in this figure, an optical diffraction grating 9 and a light receiving array 10 are used instead of the wavelength tunable optical filter 5 and the light receiver 6.
Is newly provided.

In this figure, an optical diffraction grating 9 outputs SF light (angular frequency ω1-1) output from a fundamental wave removing filter 4.
+ Ω2, ω1-2 + ω2, ω1-3 + ω2) are separated into SF light of each light wavelength, and the light receiving array 10 receives the separated SF light. Here, since the diffraction angle of the light diffraction grating 9 differs depending on the light wavelength of the incident light, each SF light is diffracted at a different angle for each wavelength. Therefore, an array type light receiving element or C
By using a CD or the like, it is possible to obtain the minimum light wavelength resolution according to the number of light receiving elements of the light receiving array 10. Further, in the present embodiment, a plurality of S
Since the F light is received at the same time, the time waveform and the optical wavelength distribution of each optical signal constituting the signal light under measurement can be measured simultaneously.

The embodiment of the present invention has been described above in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and changes in design and the like may be made without departing from the gist of the present invention. Even if there is, it is included in the present invention. For example, in the above-described embodiment, an example has been described in which the SFG is generated in the nonlinear optical crystal 3 and the waveform of the signal light to be measured is restored from the generated SF light. It is also conceivable to restore the waveform of the signal light to be measured from the generated difference frequency light.

Next, the inclusion relation between the means described in the claims,
The correspondence between the respective means and the present embodiment will be described. In the following inclusive relation, the included means (lower means) is different from the included means (higher means).
It is assumed to be described one step lower. Sampling pulse light source ... Sampling pulse light source 1 Combining means ... Optical multiplexer 2 Sum frequency light generating means Sum frequency light generating effect element ... Non-linear optical crystal 3 Removing means ... Fundamental wave removing filter 4 Light wavelength selecting means ... Wavelength tunable optical filter 5 Detecting means ... Light receiving device 6 Processing means ... Electric signal processing unit 7, display 8 Light wavelength diffracting means ... Optical diffraction grating 9 Light receiving element array ... Light receiving array 10

[0023]

As described above, according to the present invention, the optical waveform of each optical signal with high resolution can be accurately determined with respect to the signal light to be measured in which a plurality of optical signals having different wavelengths are wavelength-multiplexed. Can be measured. Further, according to the present invention, it is possible to accurately measure not only the optical waveform of each optical signal but also the distribution of the optical wavelength region. Further, by using the light wavelength diffraction means and the light receiving element array, the light time waveform and the light wavelength distribution can be measured simultaneously.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an optical sampling waveform observation device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the principle of generation of sum frequency light in the embodiment.

FIG. 3 is a block diagram illustrating a configuration example of an optical sampling waveform observation device according to a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a conventional optical sampling waveform observation device.

[Description of Signs] 1 ... Sampling pulse light source, 2 ... Optical multiplexer, 3
…… Non-linear optical crystal, 4 …… Fundamental wave removal filter, 5
... Tunable optical filter 6... Photodetector 7... Electrical signal processing unit 8... Display 9.
10 ... Light receiving array

Claims (9)

[Claims] 1. A sampling pulse light source for outputting a sampling pulse light having a wavelength different from each optical signal to a signal light to be measured in which a plurality of optical signals having different wavelengths are wavelength-multiplexed; Multiplexing means for multiplexing light and the sampling pulse light, inputting the output light of the multiplexing means, and sum frequency light of each of the wavelength-multiplexed optical signals and the sampling pulse light,
Sum frequency light generating means for outputting corresponding to each optical signal; and light wavelength selection for selecting and outputting only sum frequency light of a specific wavelength among sum frequency lights output by the sum frequency light generating means. Means, detecting means for detecting the sum frequency light output from the light wavelength selecting means, and restoring an original optical signal corresponding to the sum frequency light based on the sum frequency light detected by the detecting means. An optical sampling waveform observation device, comprising: processing means. 2. The optical sampling waveform observation device according to claim 1, wherein the optical wavelength selection means changes the wavelength of the sum frequency light to be selectively output to an arbitrary value. 3. A sampling pulse light source for outputting a sampling pulse light having a wavelength different from each optical signal to a signal light to be measured in which a plurality of optical signals having different wavelengths are wavelength-multiplexed; Multiplexing means for multiplexing light and the sampling pulse light, inputting the output light of the multiplexing means, and sum frequency light of each of the wavelength-multiplexed optical signals and the sampling pulse light,
Sum frequency light generating means for outputting corresponding to each optical signal; light wavelength diffracting means for diffracting the sum frequency light output by the sum frequency light generating means at different angles for each light wavelength; A light-receiving element is arranged in an array, a light-receiving element array for receiving each sum-frequency light diffracted by the light wavelength diffracting means, and each sum-frequency light based on each sum-frequency light detected by the light-receiving element array. Processing means for restoring the original optical signal corresponding to (1). 4. The optical sampling waveform observation device according to claim 1, wherein the sum frequency light generating means includes: a sum frequency light generating effect element for generating the sum frequency light; An optical sampling waveform observation device, comprising: a removing unit that outputs only sum frequency light. 5. A sampling pulse light source for outputting a sampling pulse light having a wavelength different from each optical signal to a signal light to be measured in which a plurality of optical signals having different wavelengths are wavelength-multiplexed; Multiplexing means for multiplexing light and the sampling pulse light, and inputting the output light of the multiplexing means, the difference frequency light between each of the wavelength-multiplexed optical signals and the sampling pulse light,
A difference frequency light generating means for outputting corresponding to each of the optical signals; and an optical wavelength selection means for selecting and outputting only a difference frequency light of a specific wavelength from among the difference frequency lights output by the difference frequency light generating means. Means, detecting means for detecting the difference frequency light output from the light wavelength selecting means, and restoring an original optical signal corresponding to the difference frequency light based on the difference frequency light detected by the detecting means. An optical sampling waveform observation device, comprising: processing means. 6. The optical sampling waveform observation device according to claim 5, wherein the optical wavelength selection means changes the wavelength of the difference frequency light to be selectively output to an arbitrary value. 7. A sampling pulse light source that outputs a sampling pulse light having a wavelength different from each optical signal to a signal light to be measured in which a plurality of optical signals having different wavelengths are wavelength-multiplexed; Multiplexing means for multiplexing light and the sampling pulse light, and inputting the output light of the multiplexing means, the difference frequency light between each of the wavelength-multiplexed optical signals and the sampling pulse light,
A difference frequency light generating unit that outputs corresponding to each of the optical signals; a light wavelength diffraction unit that diffracts the difference frequency light output by the difference frequency light generating unit at a different angle for each light wavelength; A light-receiving element is arranged in an array, a light-receiving element array for receiving each difference frequency light diffracted by the light wavelength diffracting means, and each difference frequency light based on each difference frequency light detected by the light-receiving element array. Processing means for restoring the original optical signal corresponding to (1). 8. The optical sampling waveform observation device according to claim 5, wherein the difference frequency light generating means includes: a difference frequency light generating effect element that generates the difference frequency light; An optical sampling waveform observation device, comprising: a removing unit that outputs only difference frequency light. 9. The optical sampling waveform observation device according to claim 1, wherein the sampling pulse light source selects a wavelength of the sampling pulse light output from the sampling pulse light source to an arbitrary value. An optical sampling waveform observation device, characterized in that: