JPS5961723A - Light spectrum analyzer - Google Patents

Abstract

PURPOSE:To enable a high speed photometry of emission spectrum or the like by changing the sweep of wavelength from mechanical system to electric system with a multi-channel type detector in a unidimensional array to enable a high speed sweep while a memory is built into the equipment. CONSTITUTION:A measuring light is introduced into a spectrometer 23 through an optical fiber 21 and the positioning between an incident slit 24 of the spectrometer 23 and the optical fiber 21 is done with an XYZ fine adjustor 22. Light passed through the incident slit 24 is analyzed into spectrum and enters a photodiode array 30. Bits of the array 30 and the wavelength are detected corresponding to each other. A control signal is provided to the X axis of an oscilloscope 33 from a timing control circuit to always monitor the light spectrum. The input to the oscilloscope 33 is switched at the output in a selector and data in an RAM is displayed on the oscilloscope 33. This enables a high speed photometry of emission spectrum of a light emitting element and the observation of changes in the time series.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical spectrum analyzer for, for example, analyzing the emission spectrum of light emitting elements such as lasers and LEDs, and analyzing the spectra of optical fibers and interference filters. .

Conventional configurations and their problems In recent years, for example, in the development of semiconductor lasers, and in the technical fields of semiconductor laser applications such as optical sensors, optical recording, and optical communications, improvements in performance and reliability have been made. A family 4111 device for dynamically changing the emission spectrum of a semiconductor laser is currently in demand.

A conventional optical spectrum analyzer will be explained below.

Fig. 1 shows an example of the configuration of a conventional optical spectrum analyzer, in which 1 is an optical fiber, 21-J is an X Y Z fine movement device, 3 is a dispersive separator, 4 is an input "slit", and 6 is a dispersion type separator.
is a plane mirror, 6 and 7 are concave mirrors, 8 is a diffraction grating, 9 is a rotating glass plate, 1o is an output pickpocket 71, 11d1 is a manual rotation device for the diffraction grating 8, 12 is a photomultiplier tube, and 13 is a photomultiplier tube. A high-voltage power supply, 14 a preamplifier, 15 a trigger circuit, and 16 an onroscope.

The operation of the conventional spectral analyzer having the following configuration will be described below.

The measurement light is guided by an optical fiber 1 to an entrance slit 4 of a spectrometer 3. The positioning is performed by an XYZ fine movement device 2. Input slit 41d: narrows down by KT@ to improve zero resolution.

The light passing through the entrance slit 4 is sent to a concave mirror 6 and a plane mirror 6.
The light is guided to the diffraction grating 8 through nl, where it is separated into light having a diffraction angle corresponding to the wavelength and the incident angle fL. The diffracted light is imaged on the exit slit 10 by the concave mirror 7, and its light intensity is detected by the photomultiplier tube 12 behind it.
Selection and sweeping of the detection wavelength are performed using a concave mirror 7 and a photomultiplier tube 1.
This is done by a rotating glass plate 9 and an exit slit 10, which are placed between the two. That is, the reflected light from the concave mirror 7 enters the rotating glass plate 9, where it is roughly refracted and guided to the output beam 10. However, since the image is formed at a position corresponding to the wavelength, the wavelength can be selected by closing the exit slit 10' (z).

FIG. 2 is an enlarged view of the emission section of a conventional optical spectrum analyzer, and shows how the wavelength is selected as described above. In the figure...λ1.・・・・・・λ2. ...λ3
... indicates the wavelength of light, here, λ
The light intensity of two wavelengths is detected. The detection wavelength is swept by rotating the rotating glass plate 9 and changing the refraction angle. The rotation of the rotating glass plate 90, that is, the sweeping of the wavelength, is performed by the trigger circuit 15. Detected by photomultiplier tube 12 1. The light is converted into an electrical signal
The signal is then sent to the oscilloscope 16.

The oscilloscope 16 is swept by the trigger circuit 16. The light spectral distribution is displayed! Sign.

Note that the analysis wavelength range can be performed by changing the angle of incidence on the diffraction grating 8 using the rotation device 11.

However, with conventional optical spectrum analyzers, J-
As described above, since the wavelength sweep is performed using a mechanical sweep method in which the rotating glass plate 9 is rotated, high-speed sweeping is difficult.

Therefore, for example, it is not effective for analyzing high-speed changes such as mode jumping phenomena in semiconductor lasers. Currently, commercially available optical spectrum analyzers analyze optical spectra in a steady state with a non-sweep IW of several tens of milliseconds to several seconds.

Purpose of the Invention The present invention solves the problem described in 1. For example, it makes it possible to analyze the spectrum of high-speed changes such as the mode jump phenomenon of semiconductor lasers that occurs during disturbances such as temperature or reflective objects or during modulation. An object of the present invention is to provide an optical spectrum analyzer that performs

Structure of the Invention The optical spectrum analyzer of the present invention includes a dispersive spectrometer, a multimode optical fiber for guiding measurement light to the spectrometer, An XYZ fine movement device for aligning the position with the slit, and a one-dimensionally arrayed multi-channel optical detector H- arranged on the imaging plane on the output side of the spectrometer in alignment with the spectral plane, as described in -42. It is equipped with a signal processing circuit that inputs the output of the photodetector and displays the entire optical spectrum on the oscilloscope.With this configuration, the spectral plane is placed on the imaging plane on the output side of the spectrometer. Together, to the mouth of the one-dimensional array.
Since all channel type photodetectors have been installed, the wavelength sweeping method can be changed from an all-mechanical method to an electrical method V? - It has the advantage of being able to perform high-speed sweeping, which was not possible with conventional mechanical sweeping methods.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 shows the configuration of the actual side of the optical spectrum analyzer of the present invention. In FIG. 3, C121 is a multimode optical fiber, 221. ．． 1', XYZ fine movement device, 23 is an asymmetrical deformed zerny with a focal length of 5 oomm.
Turner mount type dispersive spectrometer, 24 is an entrance slit, 25 is a plane mirror, 26 and 27 are concave mirrors, 28 is a diffraction grating with 1200 grooves/shape and a blaze wavelength of 750,
29 is a manual rotation device of a diffraction grating, 3o1d, a self-sweeping one-dimensional array silicon photodiode array (Pig;
257z.

The number of bits (elements) is 1512), 31 is a signal processing circuit with a built-in CPU, and 32 is a 16 KB memo IJ-133 is an oscilloscope.

Figure 4 shows the magnification of the output part of the optical spectrometer 23 in Figure 3, 30J: ↓ the light receiving part of the photodiode array 30,
It is a terminal up to 30″l.
. . . λ3 . . . indicates all possible wavelengths. Photodiode array 3Q is )Y, min-)Y
, are arranged so that the spectral H direction and the array arrangement direction '1 (r) coincide with the imaging plane I on the output side of the photodiode array 3Q, and each bit of the photodiode array 3Q and the wavelength of the light are aligned in that direction. 1
correspond. Note that there is a first
There is no exit slit that is present in conventional optical spectrum analyzers as shown in the figure.

Figure 6 shows the signal processing circuit 31 and memory 32 in Figure 3.
This figure shows a circuit block diagram of the circuit.

In the figure, 40 is a drive circuit for the photodiode array 30;
1 and 42 are the same output gain control circuit, 4
3 and 44 are the same A/D converter (8 bits), 4
5 is a selector, 46 is a D/A converter, 47 is an amplifier, 48 is a selector, 49 is a 1sKB (32 screens) RAM (corresponds to 32 in Figure 3), 60 is a selector, 5
1 is an address counter, 62 is a timing control circuit, 53 is Ilo for the device built-in circuit, and 64 is a CPU.
(ZaO), 66 is an interface for connection with an external CPU, 66 is a panel switch, and 57 is a power supply.

The entire operation of the optical spectrum analyzer of this embodiment configured as described above will be explained below.

First, in FIG. 3, measurement light is guided 12 to a spectrometer 23 through an optical fiber 21. At that time, the alignment of the input Surino I 24 of the spectrometer 23 and the optical fiber 21 is x
This is done using the YZ fine movement device 22. Entrance slit 24
The light that has passed through 7 is spectralized in the spectroscope and then enters the photodiode array 30. This will be explained below using FIG. 4.

The output of the photodiode array 23 (the spectral direction and the arrangement direction of the array are completely aligned on the imaging plane 11), and the photodiode array 23
Each of the 30 digits (1st bit,..., N bit, 512th digit) and the four branches of light (λ1,..., λ2,... .

The signal processing section will be explained below using FIG. The f1711 signal 11 of the photodiode array 3o is performed by the timing control circuit 52.

The output of each bit of the photodiode array 3o is optical intensity 1
The product of Lj and the integral time (between 4 irradiation ports) is Lj, and the integral time (do.5 msec, 1 msec, 2 m
sec, 5msec.

The panel switch 56 can select six stages of 1 omsec. The time for one sweep of 512 bits of the photodiode array 30 is o. It is set to 5msθC.

Now, a sweep start signal is input from the timing control circuit 52 to the self-sweeping photodiode array 30.
Then, it takes O-5 msec and 512 h'zl. of outputs are sequentially transferred, and when the output transfer is completed, the transfer is automatically stopped. It should be noted that the pintos that have been fully transferred will start printing in sequence. The sweep start signal is repeated at intervals of the integration time. In addition, photodiode array 3.

The output is taken out by separating all the odd numbered bits and even numbered bits, and then the gain control circuits 41 (42) and A
/D converter 43 (44) (through selector 4
5, the signals are rearranged in time series and applied to the Y-axis of the oscilloscope 33 (7) via the D/Afm device 46 and amplifier 47. On the other hand, a suppressing signal is applied to the X axis of the onroscope 33 from a timing control circuit 62, so that the entire optical spectrum can be constantly monitored. The digital signal of the selector 46 is monitored by the oscilloscope 33, and at the same time, the RA of 16 KB (equivalent to 32 screens) is sequentially removed and changed to 2" to the M49, and the rewriting in the RAM 49 is stopped from the panel switch 56. By sending signals, data for 32 screens of time can be held.The above-mentioned stop number is selected when all the buttons are selected.Writing to and reading from the RAM 49 is performed by the address counter 51. It's getting better.R
The data held at Kawasagomi 1'i'L on AM49 is,
By sending a command for reading from the panel switch 56, the input to the onroscope 33 is input to the selector 4.
Switching from output 5 to output 1 of selector 48,
Data in RAM 49 can be displayed on oscilloscope 33. Furthermore, 'l' of 32 screens in RAM49! +Display of fixed picture quotient, or], the speed at which the visual system can follow the entire 332-picture screen sequentially [-It is possible to repeatedly display C) In addition, the interface 55VC is external cPU
An example of #171il1 using the optical spectrum analyzer of the present invention is shown in Figure 6 and b. The entire emission spectrum of a near-infrared semiconductor laser with a strong self-coupling effect.
-1 measurement and drawn using an external CPUi. When the integration time is set to 10 msec, b is the integration time sound. J5
This is when it is set to msec. In the figure, the vertical axis is light intensity, and the horizontal axis is light wavelength.

In a, there are three spectra, which indicates that two or three spectra exist at the same time (multimode), but in b, it is shown that three spectra do not exist at the same time. It shows. In other words, this shows that a single-mode to double-mode jump occurs. In this way, the phenomenon becomes clear through high-speed photometry.

In this way, a dispersive spectrometer, a multi-mode optical fiber for guiding measurement light to the spectrometer, and an XYZ fine movement device for aligning all the output light of the optical fiber with the input slit of the spectrometer; A one-dimensionally arrayed multi-channel photodetector is placed on the imaging plane on the emission side of the spectrometer, and the optical spectrum is displayed on an oscilloscope using the output of the photodetector as input. Natsu/Lock M
), it is possible to change the wavelength sweep from a mechanical method to an electrical method.
This) shows that the conventional machine 1 &2'L sweep force type can't obtain 2'L.
Is it possible to perform a very high speed sweep? :I have something to do. Moreover, the signal processing circuit includes the gain control circuit of the ℃ detector described in 1-) and the analyzer of the gain control circuit described in 1-
J (converts the li output to a fully digital signal/ζth A
a /D converter, a memory having a storage capacity of data for at least the array bits of the I-detector for recording the output of the A/D converter, and the output of the photodetector or the memory. a D/A converter for converting the data into analog and sending it to the Y axis of the oscilloscope;
The photodetector, the above D/A converter, the L A/D converter, the memorandum memory, the timing control circuit for measuring the Xilil band of the above oscilloscope, and for opening the entire device. It is equipped with an interface that allows connection between the CPU of be.

In the above embodiment, a diode array was used as the photodetector, but it should be noted that a COD image sensor may also be used instead.

Effects of the Invention As described above, the main feature of the present invention is to use a multi-channel detector with a -dimensional array and change from a completely mechanical wavelength sweep method to an electrical method (by which the conventional mechanical sweep method can be changed). It has the advantage of enabling high-speed sweeping, which was not possible with conventional methods, and by incorporating memory into the device, it is possible to perform high-speed photometry of the emission spectrum of light-emitting elements, and to observe time-based Tll changes.

[Brief explanation of the drawing]

Figure 1 is a (1♂) component block diagram of a conventional optical spectrum analyzer, Figure 2 is an enlarged view of the output section of the spectrometer of the same equipment, and Figure 3 is an embodiment of the optical spectrum analyzer of the present invention. FIG. 4 is an enlarged view of the output section of the spectrometer of the same device, FIG. 6 is a block diagram of the signal processing circuit and part of the memory of the same device, and FIG. It is a figure showing t1 side inversion by an optical spectrum analyzer. 21...Optical fiber, 22...XYZ
Fine movement device, 23... Spectrometer, 30... Photodimade array, 31... Ibo processing circuit,
32...Memory, 33...Oscilloscope. Name of agent: J-Flj member Toshio Nakao and 1 other person
given name. ('np)
SN”fu [n p) SN ko Wf

Claims (1)

[Claims] (1) a dispersive spectrometer, a multi-mode optical fiber for guiding measurement light to the spectrometer, and positioning the output light of the optical fiber in item 1 to the input slit of the spectrometer. xYZ fine movement device for
A one-dimensional array of multi-channel photodetectors arranged on the imaging plane of 1 according to the spectral plane, and signal processing for displaying the optical spectrum on the onroscope using the output of the source stopper as input. An optical spectrum analyzer equipped with a circuit. (9)) The signal processing circuit includes a gain control circuit for the photodetector, and an A/D converter for converting the analog signal output of the gain control circuit into a fully digital signal;
A memory for recording the output of the A/D converter and having a storage capacity of at least as much data as the array bits of the photodetector (for both sides), and the output of the photodetector or the data in the memory. a D/A converter for converting the signal into an analog signal and sending it to the Y axis of the oscilloscope; the photodetector; the A/D converter; the D/Aff converter; Claim No. 1, characterized in that the device is equipped with a timing control circuit for controlling the X-axis sweep, a CPU for controlling the entire device, and an interface for making connection with an external CPU possible. The optical spectrum analyzer according to item 1.