JPH02198367A - Optical spectrum analyzer - Google Patents

Abstract

PURPOSE:To secure high resolution and high reliability with an apparatus characterized by simple manufacturing and an excellent yield rate by providing four bulk type lenses, a compact lightguide board, a light source whose position is readily adjusted, and a light detecting array. CONSTITUTION:This analyser is composed of the following parts: a laser diode 31 which is sealed in an airtight manner; a two-dimensional lightguide board 33 wherein a surface elastic wave converter 32 is arranged; bulk type first - fourth lenses 35 - 38; and detecting array. The laser light from the diode 31 is converted into the parallel light through the first lens 35. The light becomes a beam having a long elliptical cross section through the second lens. The beam is inputted into the board 33. The light in the vertical direction is confined in the lightguide with the board 33 and propagated, while the parallel light is diffracted with the surface elastic wave from the converter 32 in response to an RF signal and propagated. The light is guided to the array 34 through the third and fourth lenses 37 and 38. The change in position of the light condensing point in diffraction and the change in intensity of the light are detected. Since it is not necessary to provide the lenses on the same board as with the converter in this apparatus, the board can be made compact, and it is not necessary to fix the detecting array on said board directly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical spectrum analyzer that analyzes an RF multiplied signal spectrum using laser light.

(Prior art) Documents describing optical spectrum analyzers include: (1) Ohmsha's "Optical Integrated Enclosure" Authors Hiroshi Nishihara, Masamitsu Haruna, Toshiaki Narahara (2) D. Mergerlan, c, a'0p
erational 1integrated optl
cal RFspectrum analyzer Appl, Opt, 19, 18. p, 3033
．． 5ept, 1980 (3) T, 5uhara,
e,a'A folded-type Integr
ated-optlcSpectruffle anal
yzer using butt-coupledch
irped gratlng 1ensesIEE
E. J., Quantum Electron.

QE-18, 7, p, 1057. July 19
82 is given. This document describes a type using a geodesic lens as shown in FIG. 2, and a folded type using a reflective chirb grating lens as shown in FIG.

Briefly, the optical spectrum analyzer shown in FIG. Geodesic lenses 13, 14 are formed.

In this optical spectrum analyzer, a laser beam emitted from a laser diode 1B attached to one end of an optical waveguide 12 is made incident on the optical waveguide 12, and this laser beam is guided to a first geodesic lens 13 to convert it into parallel light. It is converted and input into the Bragg cell 11. The surface acoustic wave transducer 15 generates an elastic wave according to the input RF signal,
Add perpendicular to the above parallel light. The light incident on the Bragg cell 11 is diffracted by this elastic wave. The diffracted light output from the Bragg cell 11 is guided to a second geodesic lens 14 and focused on a photodetector array (image sensor) 17 attached to the other end of the leading waveguide 12. Here, if the distance of the diffracted light to the diffracted light is measured by the photodetection array 17, the RF multiplied signal frequency component can be determined, and if the light intensity is measured, the RF multiplied signal power can be determined.

The optical spectrum analyzer shown in Fig. 3 is Tl:LiN
A surface acoustic wave transducer 23 is formed in an optical waveguide 22 made of bO3. In this optical spectrum analyzer, laser light emitted from a laser diode 24 attached to one end of the optical waveguide 22 is incident on the optical waveguide 22, and this laser light is transmitted to a laser diode 24 attached to the other end of the optical waveguide 22. 1 reflective chirve grating lens 2
5, the light is reflected at an angle φ with respect to the optical axis g to become parallel light, and the light is made incident on the Bragg cell 21. The surface acoustic wave transducer 23 generates an elastic wave according to the input RF signal and applies it perpendicularly to the parallel light. The parallel light incident on the Bragg cell 21 is diffracted by this elastic wave.

The diffracted light is guided to the second reflective chirb grating lens 2B and is directed to a photodetection array (image sensor) 27 attached to the other end of the leading waveguide 22 at an angle ma with respect to the optical axis g'. The light is focused.

Here, by measuring the distance of the diffracted light with respect to the diffracted light using the photodetection array 27, the RF multiplied signal frequency component can be obtained, and by measuring the light intensity, the RF multiplied signal power can be obtained.

However, the optical spectrum analyzer with the above configuration has the following problems.

In the optical spectrum analyzer using the geodesic lens shown in FIG. 2, it is difficult to manufacture the geodesic lens. Furthermore, in order to improve the resolution, the optical length must be increased, but if the Bragg cell substrate is made larger, the crystallinity deteriorates, so it is difficult to produce a substrate that can increase the optical length. Furthermore, even in the folded optical spectrum analyzer using the reflective chirb grating lens shown in Figure 3, it is difficult to obtain a large substrate that can increase the optical length in order to improve resolution for the same reason as above. .

In particular, as with both analyzers, 1
Since each substrate is large, the number of substrates that can be manufactured from one wafer is small. Additionally, manufacturing errors in the optical parameters of the light source, photodetector, and lens (e.g., the divergence angle of the light source, the allowable angle of light incidence of the photodetector, the focal length of the lens, etc.) will directly lead to a decrease in the resolution of the analyzer. , there is no adjustment function that can tolerate and correct it. Furthermore, although the light source and photodetector (and chirve grating lens) are fixed directly to the optical waveguide, their materials are different, which makes it difficult to fix them reliably. After one is fixed, the other must be finely adjusted and fixed. Furthermore, in order to ensure the reliability of the light source and photodetector, the entire analyzer must be hermetically sealed with high precision. From the above, conventional analyzers have had the problems of being difficult to manufacture, unable to increase resolution, poor yield, and difficult to ensure reliability.

(Problems to be Solved by the Invention) As described above, in conventional optical spectrum analyzers, the lens is formed on the same substrate as the surface acoustic wave transducer, or the substrate is made larger and the grating lens is directly fixed. In addition, since the light source and photodetector are directly fixed, there are problems such as difficulty in manufacturing, inability to increase resolution, poor yield, and difficulty in ensuring reliability.

This invention was made in order to solve the above problems, and its purpose is to provide an optical spectrum analyzer that is easy to manufacture, has high resolution, good yield, and can easily ensure reliability. shall be.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an optical spectrum analyzer according to the present invention includes a light source that emits a light beam in a fixed direction, and a light beam that is emitted from the light source. A first lens that converts the parallel light beam into a parallel light beam, a second lens that focuses the parallel light beam converted by the first lens in one direction, and a second lens that focuses the parallel light beam in one direction by the second lens. A two-dimensional optical waveguide substrate for inputting a light beam and confining and propagating the incident light, and a surface acoustic wave disposed on the two-dimensional optical waveguide substrate in accordance with an input RF signal to propagate through the two-dimensional optical waveguide substrate. a surface acoustic wave transducer that applies the parallel light perpendicularly to the parallel light;
a third lens that focuses the light beam emitted from the two-dimensional optical waveguide substrate in the same plane as the waveguide surface of the substrate;
a fourth lens that focuses the light beam emitted from the two-dimensional optical waveguide substrate in a plane perpendicular to the waveguide surface of the substrate; and a fourth lens that receives the light focused by the third and fourth lenses. It is configured to include a photodetection array formed by arranging a plurality of light receiving elements.

(Function) In the optical spectrum analyzer with the above configuration, the light beam emitted from the light source in a certain direction is converted into a parallel light beam by the first lens, and condensed in one direction by the second lens to form a two-dimensional optical waveguide. incident on the substrate. The light incident on this two-dimensional optical waveguide substrate is confined and propagated, but at this time, a surface acoustic wave transducer vertically applies a surface acoustic wave according to the input RF signal, thereby producing an RF multiplied signal. A corresponding diffraction is performed.

The light beam emitted from this two-dimensional optical waveguide substrate is
The light is focused in the same plane as the waveguide surface of the substrate by the lens of
Further, the light is focused by a fourth lens in a plane perpendicular to the waveguide surface of the substrate and irradiated onto the light receiving surface of the photodetection array. At this time, since a plurality of light receiving elements are arranged in the same direction as the direction of diffraction by the surface acoustic wave, it is possible to detect changes in the position of the focal point and changes in light intensity during diffraction. In this case, a bulk type lens can be used for each lens, and since it is not necessary to form the lenses on the same substrate as the surface acoustic wave transducer, the guide waveguide substrate can be small.

Furthermore, since the light source and the photodetection array do not need to be directly fixed to the substrate, their positions can be easily adjusted. Therefore, manufacturing becomes simple, resolution increases, yield is good, and high reliability can be obtained.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows its structure, in which (a) the waveguide surface is viewed perpendicularly, and (b) the waveguide surface is viewed parallel to the waveguide surface.

This optical spectrum analyzer includes a hermetically sealed laser diode 31 with a glass window, a two-dimensional optical waveguide substrate 33 on which a surface acoustic wave transducer 32 is disposed,
In addition to a photodetection array 34 using a hermetically sealed CCD with a glass window, bulk type first to fourth lenses 35 to 38 are provided.
It is equipped with:

Optical coupling between the laser diode 31 and the guide waveguide substrate 33 is performed by first and second lenses 35 and 36. The first lens 35 is an aspherical lens, and the laser diode 3
The laser beam emitted from the lens 1 is converted into parallel light and guided to the second lens 3B. The second lens 3B is a cylindrical lens that condenses light in a direction perpendicular to the surface of the waveguide substrate 33 out of the parallel light guided from the first lens 35 to generate a beam having an oblong cross section. , which is incident on the leading waveguide substrate 33.

The optical waveguide substrate 33 confines within the waveguide the light in the direction perpendicular to the surface of the incident light and propagates it, and allows the light parallel to the surface to propagate as is. In addition, this guiding waveguide substrate 3
A surface acoustic wave transducer 32 disposed at 3 applies a surface acoustic wave corresponding to the input RF multiplied signal perpendicularly to the parallel light propagating in the leading wave path, thereby causing a diffraction phenomenon of the parallel light. It is.

Optical coupling between the guide waveguide substrate 33 and the photodetection array 34 is performed by the third
and a fourth lens 37,38.

The third lens 37 is a single-sided convex lens, and the third lens 37 is a single-sided convex lens.
Of the laser light emitted from the waveguide substrate 33 , light in a plane parallel to the surface of the waveguide substrate 33 is focused on the light receiving surface of the photodetection array 34 . The fourth lens 38 is a cylindrical lens that directs light in a plane perpendicular to the surface of the waveguide substrate 33 out of the laser light guided from the leading waveguide substrate 33 via the third lens 37 to the light receiving surface of the photodetection array 34. It focuses light on

That is, in the optical spectrum analyzer having the above configuration, the laser beam emitted from the laser diode 31 is converted into parallel light having a circular cross section by the first lens 35, and is converted to a long elliptical cross section by the second lens 3B. The beam becomes a beam and enters the guide waveguide substrate 33. In this waveguide substrate 33, light in a direction perpendicular to the substrate surface is confined in the waveguide and propagated, and light in a direction parallel to the substrate surface is transmitted by a surface acoustic wave transducer 32 into which an RF multiplied signal is input. The surface acoustic wave undergoes diffraction corresponding to the RF multiplied signal and is propagated.

The laser light emitted from the optical waveguide substrate 33 passes through the third lens 37 and the fourth lens 38 to the photodetection array 34.
guided by. At this time, the light in the direction parallel to the surface of the waveguide substrate 33 is focused by the third lens 37, and the light in the perpendicular direction is focused by the fourth lens 38 on the light receiving surface of the photodetection array 34.

At this time, since a plurality of light receiving elements are arranged in the photodetection array 34 in the same direction as the diffraction direction by the surface acoustic wave,
Changes in the position of the focal point and changes in light intensity during diffraction can be detected. In this case, a bulk type lens can be used for each lens, and since it is not necessary to form the lenses on the same substrate as the surface acoustic wave transducer, the guide waveguide substrate can be small.

Furthermore, since the light source and the photodetection array do not need to be directly fixed to the substrate, their positions can be easily adjusted.

Therefore, the optical spectrum analyzer configured as described above can be easily manufactured, has high resolution, has a good yield, and can obtain high reliability.

Note that this invention is not limited to the above embodiments,
The lens system between the laser diode 31 and the two-dimensional waveguide substrate 33 does not necessarily need to be an aspherical lens or a cylindrical lens, but may be such that the laser light from the laser diode 31 is optically coupled to the two-dimensional waveguide substrate 33. Alternatively, two or more bulk lenses, such as a single-sided convex lens, may be used to condense light in one direction. Similarly, the lens system between the two-dimensional waveguide substrate 33 and the photodetection array 34 does not necessarily need to use a single-sided convex lens or a cylindrical lens; Two or more bulk lenses may be used as long as the beam is focused.

Furthermore, the light source may be any light source that can emit coherent light of a wavelength that can propagate in the leading wavepath without using the laser diode 31. Further, the photodetection array may be of any type as long as it can detect the position of the diffracted light corresponding to the RF multiplied signal.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an optical spectrum analyzer that is easy to manufacture, has high resolution, has a good yield, and can easily ensure reliability.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the optical spectrum analyzer according to the present invention, in which (a) the figure is viewed perpendicularly to the waveguide surface, and (b) the figure is the view parallel to the waveguide surface. 1, FIG. 2, and FIG. 3 are configuration diagrams showing the configuration of a typical conventional optical spectrum analyzer, respectively. 31... Laser diode, 32... Surface acoustic wave transducer, 33... Two-dimensional optical waveguide substrate, 34
... Photodetection array, 35... First lens (aspherical lens), 3B... Second lens (cylindrical lens),
37...Third lens (single-sided convex lens), 38...
Fourth lens (cylindrical lens).

Claims (1)

[Claims] A light source that emits a light beam in a fixed direction, a first lens that converts the light beam emitted from this light source into a parallel light beam, and the parallel light beam converted by the first lens is focused in one direction. a two-dimensional optical waveguide substrate that receives a light beam focused in one direction by the second lens, confines the incident light, and propagates the two-dimensional optical waveguide substrate; a surface acoustic wave transducer that applies a surface acoustic wave according to an input RF signal perpendicularly to the parallel light propagating in the two-dimensional optical waveguide substrate; a third lens that focuses the light beam in the same plane as the wavefront; a fourth lens that focuses the light beam emitted from the two-dimensional optical waveguide substrate in a plane perpendicular to the waveguide surface of the substrate; An optical spectrum analyzer comprising a photodetection array including a light receiving element that receives light focused by third and fourth lenses.