JPH02156124A - Light wavelength analyzing/measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a measuring apparatus in noway depending on the polarization of an input light with a compact construction having only one photo detector by arranging a beam splitter, a polarization control means, a diffraction rating and a detector. CONSTITUTION:A polarized beam splitter 100 separates an input light in a double polarization orthogonal spatially. A polarization holding fiber 102 makes one light separated in the double double polarization with the polarization state of the other light as polarization control means 400. A diffraction grating 2 performs a wavelength analysis on an output light of the polarization control means 400 and the other light not passing through the polarization control means 400. A photo detector 4 detects a diffraction light power of the diffraction grating 2. Thus, the polarized light incident into the diffraction grating 2 is made constant thereby enabling the correction of a diffraction efficiency of the diffraction grating 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measurement device for measuring the emission spectrum and spectrometry of semiconductor lasers and the like.

[Conventional technology]

In conventional optical wavelength-resolved measurement devices, input light is generally wavelength-resolved using a diffraction grating, and this light is measured with a photodetector to perform optical wavelength-resolved measurement. In such an optical wavelength resolution measuring device, the output light level changes because the diffraction efficiency of the diffraction grating is wavelength dependent and polarization dependent (the diffraction efficiency is different for TE light and TM light with respect to the diffraction grating). (M, G, Moharam
et al, “Rig.

rous coupled-wave analysis
sis of metallic 5urfac
e-relief greetings” Journa
l of 0ptical 5ocieLy of A
merica, vol, 3. No, 11. PP1780
-1787.1986) The wavelength dependence of diffraction efficiency can be easily calibrated if the measurement wavelength is known. but,
Regarding polarization dependence, the polarization state of input light is often unknown. In particular, when input light passes through a single mode optical fiber, its polarization state is unknown unless it is measured. In this case, in order to calibrate the polarization state of the input light, the output light of the diffraction grating is polarized by a polarization beam splitter, which is detected by a separate photodetector, and then a correction calculation is performed. Optical wavelength resolving measurement devices without dependence have been manufactured (for example, Anritsu Optical Spectrum Analyzer MS9001B1).

[Problem to be solved by the invention]

The above-mentioned optical wavelength-resolving measuring device has the disadvantage that a plurality of photodetectors are required to separate the polarized light after the wavelength is resolved by the diffraction grating, resulting in a large device.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to
An object of the present invention is to provide an optical wavelength resolving measurement device that has a compact configuration and does not depend on the polarization of input light.

[Means to solve the problem]

The optical wavelength resolving measurement device of the present invention includes a polarization separation element that separates input light into two spatially orthogonal polarization states, and a polarization splitter that makes one of the two polarization states match the other polarization state. A configuration comprising: a control means; a diffraction grating that simultaneously performs wavelength decomposition of the output light of the polarization control means and one of the lights that has not passed through the polarization control means; and a detector that detects the power of the diffracted light of the diffraction grating. This is an optical wavelength resolving measurement device characterized by being able to correct the diffraction efficiency of the diffraction grating by keeping the input polarization to the diffraction grating constant.

[Effect]

In the optical wavelength resolving measurement device of the present invention, input light is first separated into two orthogonal polarization states by a polarization beam splitter. One of the lights separated into two polarization states is polarized by a polarization controller, which is a polarization control means, and converted into light in the other separated polarization state. As a result, these two polarization-separated lights have the same polarization state. Thereafter, these two lights are simultaneously wavelength-separated by a diffraction grating. In such measurements, the polarization state of the input light to the diffraction grating is constant, so even if the polarization of the input light to the optical wavelength resolution measurement device is arbitrary, the input polarization dependence of the diffraction grating will not affect the output level. Measurements can be made that do not occur.

〔Example〕

FIG. 1 shows a configuration diagram of an embodiment of the present invention. In this embodiment, input light 200 is split into two orthogonal linearly polarized components by a polarizing beam splitter 100.

Each polarized light component is then transferred to polarization maintaining fiber 101.
102. One polarization-maintaining fiber 102 is spatially twisted by 90 degrees as a polarization control means 400 so as to output the same linearly polarized light as that of the polarization-maintaining fiber 101. These polarization-maintaining fibers 101 and 102 are arranged in the direction of TE polarization with respect to the diffraction grating, so that the output light from the optical fibers becomes TE polarization with respect to the diffraction grating. In this case, the diffraction efficiency η of the diffraction grating becomes ηTE, and by calibrating with this value, the input optical power can be measured without being affected by the polarization dependence of the diffraction grating. Also at this time,
The output light 300 of the diffraction grating produces interference fringes in the longitudinal direction of the slit 103, but the output light 300 is cut by the linearly spread slit 103, and all the power of this output light 300 is received using the photodetector 4. As a result, wavelength-resolved measurements can be performed without being influenced by polarization dependence or interference fringes.

This embodiment has various modifications. As a polarization control means for converting one polarized light into the other polarized light, a Faraday rotator can be used, or a polarization control element using a LiNb09 crystal can be used. Furthermore, the incident polarization state to the diffraction grating can be any polarization state, and is not limited to TE polarization.
It may be 7M polarized light or other linearly polarized light, or it may be circularly polarized light, but in this case, it is necessary to calibrate the output power based on the diffraction efficiency for that polarization state.

In addition, the method of combining light with the same polarization state is not only by arranging the ends of optical fibers spatially, but also by mixing the light emitted from each optical fiber with a multiplexer such as a half mirror, and then combining the light with a diffraction grating. You can also enter . At this time, no interference fringes are generated on the slit.

[Effects of the Invention] As explained above, according to the present invention, by measuring the polarization state of input light as a constant, it is possible to easily compensate for the shoulder wave dependence of the diffraction efficiency of the diffraction grating, and to After wavelength decomposition, the polarization dependence of the diffraction efficiency of the diffraction grating can be easily calibrated with a simple configuration of only one photodetector.

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[Brief explanation of the drawing]

FIG. 1 is a diagram of an optical wavelength-resolving measurement device that is a typical embodiment of the present invention. In the figure, 2... Diffraction grating, 103... Slit, 4... Photodetector, 100... Polarizing beam splitter, 101,
102...Polarization maintaining fiber, 200...Input light,
300: Output light; 400: Polarization control means.

Claims (1)

[Claims] a polarization separation element that separates input light into two spatially orthogonal polarization states; a polarization control device that makes one of the light separated into the two polarization states match the other polarization state; and an output of the polarization control device. An optical wavelength resolution measurement device comprising: a diffraction grating that simultaneously performs wavelength resolution of light and one of the lights that has not passed through the polarization control means; and a detector that detects the power of the diffracted light of the diffraction grating. .