JPH0439632A - Light amplifier - Google Patents

Abstract

PURPOSE:To use an optical coupling method based upon a two-lens system and to improve optical coupling efficiency by arranging an optical element for correcting an optical path between the 1st and 2nd lenses in an optical coupling two-lens system. CONSTITUTION:An optical input from an optical fiber 4a is converted into parallel beams by the 2nd lens 16a, converged into the 1st lens 11a through an optical element 17a and then coupled with a light amplifying element 1. An optical output amplified by the element 1 is converted into parallel beams by the 1st lens 11b, converged by the 2nd lens 16b through an optical element 17b and coupled with an optical fiber 4b. Parallel glass plates, two wedge-type glass plates, or the like are used as the optical elements and the optical path of the lens system is corrected by adjusting the thickness, refractive index, incident angle, etc., of the elements. Since highly efficient optical coupling can stably be obtained, >=20dB light amplification can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical amplifying device using a semiconductor optical amplifying element, and particularly to an optical amplifying device used for optical network communication, broadband optical communication, etc.

C. Prior Art] Conventional optical amplification devices are described in C.L.E.O., 1989, F.M.-3, pp. 426 to 42.
7 pages (CLEo, 1989.FM-3゜pp, 426~
As discussed in 427), an optical coupling system using a bulbous fiber is used on both the optical signal input side and the output side of an optical amplification element.

[Problem to be solved by the invention]

The above-mentioned conventional technology uses an optical coupling method using a spherical fiber, but the optical coupling efficiency is limited to about 40% due to aberrations of the spherical fiber.

In order to increase the optical coupling efficiency, it is possible to adopt an optical coupling method using a two-lens system, but in this case, the number of optical elements increases, making it easy for the optical axis to shift, which deteriorates the optical coupling efficiency. There is a problem in that it can cause

An object of the present invention is to provide an optical amplification device that uses an optical coupling method using a two-lens system and can increase the optical coupling efficiency.

Other objects of the present invention are to improve the thermal and mechanical stability of optical coupling, to selectively pass only light of a predetermined wavelength, and to have a function of monitoring light intensity. An object of the present invention is to provide an optical amplification device with a simple configuration.

[Means to solve the problem]

In order to achieve the above object, the present invention has the following features.

An optical element for correcting the optical path is arranged between the first lens and the second lens of the two-lens system for optical coupling. For example, a parallel glass plate, two wedge-shaped glass plates, etc. can be used as this optical element, and its thickness, refractive index,
The configuration is such that the optical path is corrected by adjusting the incident angle and the like.

Also, to reduce noise in optical amplification equipment.

The above-mentioned optical element has an optical filter function and is configured to allow only light of a predetermined wavelength to pass through.

Furthermore, a light-receiving element for detecting the intensity of reflected light from the optical element is arranged, and the structure has a function of monitoring the light intensity.

In addition, in order to improve thermal and mechanical stability, the optical amplification element and the first lenses on the Rokka side and Hatakeka side are integrated on a subcarrier, and this subcarrier is used as an electronic cooling element. Place it fixedly on top.

The configuration is such that the entire subcarrier can be cooled.

[Effect]

The optical element corrects the optical path deviation by changing the optical path by an amount corresponding to a predetermined size, refractive index, and angle of incidence.

Also, for thermal fluctuation 2 mechanical stress.

Since the optical amplification element and the two first lenses move together on the subcarrier, fluctuations in the relative position of the optical amplification element and the first lens are reduced, and as a result, optical axis deviation and focal deviation are reduced. becomes smaller. Also.

By operating the electronic cooling element arranged under the subcarrier, it is possible to maintain the subcarrier at a constant temperature and to reduce the above-mentioned deviations due to thermal fluctuations.

Furthermore, by providing an optical element placed between the first and second lenses with an optical filter function that allows only light with a predetermined wavelength to pass through, the noise of the optical amplification device can be reduced. . Furthermore, by providing a light receiving element that detects the intensity of reflected light from the optical element, it becomes possible to monitor the light intensity by observing the electrical signal detected by the light receiving element.

〔Example〕

A first embodiment of the present invention is shown in FIGS. 1(a) and 1(b).

This will be explained using (c). (a) is a top view (partially shown as a developed sectional view) of the device of this embodiment, (b7) is an enlarged view of the vicinity of the subcarrier, and (c) is a side view. In FIG. 1, 1 is a semiconductor optical amplification element.

2 is the waveguide, and 3 is the thermistor for temperature measurement.

4a and 4b are single mode optical fibers. Light input through the optical fiber 4a with the ferrule 18a is converted into parallel light by the second lens 16a, passes through the optical element 17a, and is focused by the first lens lla.

It is coupled to the optical amplification element 1. The optical output amplified by the optical amplification element 1 is converted into parallel light by the first lens llb,
The light passes through the optical element 17b, is focused by the second lens 16b, and is coupled to the optical fiber 4b with the ferrule 18b.

The procedure for assembling this device will be described below. First, an optical amplifying element 1 with a submount 6 is mounted on a subcarrier 9. Thermistor 3. After attaching the stud 7, attach the lens holder 10.
First lenses lla and llb are attached together with a and 10b. The first lenses 11a and llb cause the optical amplification element 1 to spontaneously emit light.

The position is adjusted so that the output light becomes parallel light and fixed at that position. The electronic cooling element 14 is attached to the bottom of the case 12, and the subcarrier 9 is fixedly attached to the electronic cooling element 14. After attaching the second lens boulders 15a, 15b to the side wall of the case 12 and inserting the second lenses 16a, 16b into the second lens boulders 15a, 15b, the optical elements 17a, 17b are attached.

The output light from the optical amplification element 1 is transmitted to the second lens 16a.

The optical element 17a is aligned with the center of the optical axis of the optical element 16b.

Adjust the refractive index 9 dimensions and arrangement of 17b. Optical element 17
An antireflection film is applied to both surfaces of each of a and 17b. Optical fiber 4a with ferrules 18a and 18b
, 4b inserted into the ferrule holders 5a, 5b are attached to the second lens boulder 15a.

Attach to 15b. At this time, the optical amplification element 1 is caused to emit light spontaneously, and the position is adjusted so that the output light from the optical fibers 4a and 4b is maximized, and the optical fiber 4a with the ferrule,
4b is soldered to the ferrule holder 5a + 5b, and the ferrule holders 5a and 5b are further welded to the second lens boulders 1.5a and 15b using a YAG laser.

A lead wire 13e is connected to the N electrode of the optical amplification element 1.

Wire bonding8. A lead wire 13f and wire bonding 8. are connected to the P electrode through the stud 7 and the submount 6. Power is supplied through the subcarrier 9. Further, the resistance value of the thermistor 3 is measured through the lead wires 13a and 13b, and a current is passed through the electronic cooling element 14L through the lead wires 13c and 13d, so that the entire subcarrier 9 can be cooled. The cooling capacity was 0°C/ampere.

The coupling efficiency of the embodiment device with such a configuration is -2 dB for both the input and output sides, and the internal gain of the optical amplifying element is 30 dB at a constant temperature of 0°C, and the amplification degree of the optical amplifying device is 26.
It was dB. Furthermore, by using three stages of the above-mentioned embodiment apparatus, transmission at 1.8 Gb/s and 180 km became possible.

FIG. 3 shows a second embodiment of the present invention, in which (a) is a top view and (b) is an enlarged view of the vicinity of the subcarrier. The optical amplifying element used in this example is an oblique waveguide type element in which the waveguide 2 is inclined by 6 degrees with respect to the perpendicular to the arm opening plane in order to reduce the reflectance at the arm opening plane. Since the light beam optically couples with this waveguide 2 at an angle of 15 degrees, the total length of the waveguide is 80 degrees.
At 0 μm, the above beam is approximately 160 μm on the input and output sides.
It shifts. For this reason, the first lens holder 10a on the input side,
The first lens lla and the first lens holder 10b on the output side
, and the first lens llb are arranged so that the distance between their respective center lines is about 160 μm. The first lens lla, llb and the second lens
By fixing parallel glass plates 19a and 19b with a thickness of 0.6 m+a and a refractive index of 1.5 between the lenses 16a and 16b so that their normals form an angle of 23.5 degrees with respect to the optical path, the nine output side It became possible to match the centers of the optical axes of the second lenses 16a and 16b, and a highly accurate optical axis alignment force 1 was achieved.

As a result, even when a diagonal waveguide type semiconductor optical amplifier was used, highly efficient optical coupling similar to that of the first embodiment was possible.

FIG. 3 is a top view of a third embodiment of the invention.

A glass plate 20 with an optical filter is disposed between the first lens 1.1b and the second lens 16b on the output side. This optical filter is a bandpass filter that transmits only light of a predetermined wavelength. Set the center wavelength of the bandpass filter to 1.
By setting the width to 55 μm and the 3 dB bandwidth to 3 nm, it was possible to reduce the noise figure of the optical amplifier to 5 dB or less. When this example element was installed before the PIN receiver, the receiving sensitivity could be improved from 10 dBm to -20 dBm.
10Gb/s, 1100k non-relay transmission is now possible.

FIG. 4 is a top view of a fourth embodiment of the present invention.

The glass plate 21 placed on the output side had an antireflection film formed only on the surface facing the second lens 16b.

A light receiving element 22 was arranged to detect the reflected light from the other surface of the glass plate 21. The light intensity was monitored by observing the output electrical signal of the light receiving element 22, and the drive current of the optical amplification element 1 was controlled so that the light intensity was constant. When this example device was used as a repeater in an optical transmission line,
If the element drive current described above is not controlled, the wavelength of the incident light will fluctuate.

The output light intensity fluctuated by 1 to 2 dB due to the polarization plane fluctuation, and the receiving sensitivity deteriorated by 1 to 2 dB, but if the above control was performed, the fluctuation range could be reduced to 0.1 dB or less. Ta.

〔Effect of the invention〕

According to the present invention, since highly efficient optical coupling can be stably obtained, optical amplification of 20 dB or more is possible.

The system can be applied to optical repeater amplifiers, optical preamplifiers, etc. Also, since optical filters, optical monitors, etc. are built-in, there is no optical loss compared to when these are housed in a separate case from the optical element. , improves optical stability, and furthermore,
This has the effect of simplifying the configuration.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram of an embodiment of the present invention, and (a) is a top view;
(b) is a partially enlarged view, (C) is a side view, FIG. 2 is a configuration diagram of another embodiment of the present invention, (a) is a top view, (b) is a partially enlarged view, and FIG. 4 are top views of other embodiments of the present invention, respectively. <Explanation of symbols> 1...Semiconductor optical amplification element 2...Waveguide 3...Thermistor 4...Single mode optical fiber 9...
Subcarrier 10... Lens holder 11a, 1
lb-first lens 12...case 14...electronic cooling element 1
6a, 16b - Second lens 17... Optical elements 18a, 18b - Ferrules 19a, 19b... Parallel glass plate 20... Glass plate with optical filter 22... Light receiving element Patent attorney Mitsuru Nakamura Junnosuke I-school filter attaching power glass plate 3 Figure 2 - Powering the flat plate 2 Figure 22

Claims (1)

[Claims] 1. In an optical amplification device using a semiconductor optical amplification element, a first lens for converting output light into parallel light and a first lens for concentrating the parallel light on at least one of the output side and the input side of the optical signal. a second lens that converts the optical signal from the input optical fiber into parallel light; and a first lens that collects the parallel light and couples it to the optical amplification element. What is claimed is: 1. An optical amplification device comprising a two-lens optical coupling system consisting of a two-lens optical coupling system, and further comprising an optical element for correcting an optical path between at least one of the first lens and the second lens. 2. An optical amplification device, wherein the optical element according to claim 1 is a parallel glass plate. 3. An optical amplification device, wherein the optical element according to claim 1 is an optical element constituted by at least two wedge-shaped glass plates. 4. An optical amplification device, characterized in that the optical element according to claim 1 is an optical element having an optical filtering effect that allows only light of a predetermined wavelength to pass through. 5. An optical amplification device characterized by having a configuration in which a light receiving element is arranged to detect the intensity of reflected light from the optical element according to claim 1, and the light intensity is monitored by the detection output thereof. 6. The two-lens optical coupling system according to claim 1 is provided on both the optical signal input side and the output side of the optical amplification element, and the optical amplification element and the first lens on the optical signal input side and the output side are connected to a subcarrier. An optical amplification device characterized by being integrated into the top. 7. An optical amplification device characterized in that the subcarrier according to claim 6 is located on a thermoelectric cooling element.