JPH01263623A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To offer a small-sized, inexpensive time-division optical switch which eliminates the need for adjustment and has a low insertion loss by forming a spatial optical switch and an optical storage element (optical memory) of compound semiconductor materials of the same kind and integrating those on a compound semiconductor substrate of the same kind. CONSTITUTION:An incidence-side optical waveguide 3 crosses four optical waveguides 21 to 24 and optical switches 11 to 14 are arranged at the respective points of intersection. The optical waveguides 21 to 24 are linked with optical memories 31 to 34 and cross a projection-side optical waveguide 4, and optical switches 15 to 18 are arranged at the points of intersection. The optical switch parts and optical memories are formed of the compound semiconductor materials of the same kind and integrated on the compound semiconductor substrate of the same kind, and they are all connected by the same optical waveguides, so those elements need not be connected newly with one another and the loss at the connection points in reducible. Further, when the optical switch parts are composed of total reflection type optical switch, etc., the time-division optical switch is realized which has no polarizing direction dependency and is easily connected to optical fibers.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical integrated circuit for exchanging optical signals as they are in optical communication, and particularly relates to an optical integrated circuit suitable for time-division optical exchange. .

〔Example〕

Optical switching systems, which exchange and process signals as they are in optical communications, are an essential technology for the realization of future ultra-high-speed, ultra-wideband switching networks. Among these, the time-division exchange method, in which the digital signals of each individual channel are time-divided on the time axis and the signal channels to be exchanged are exchanged alternately on the time axis, is expected to become the mainstream of optical exchange in the future. It is expected. The key device in this time-division optical switching system is 1×
This is a time-division optical switch that combines n and nX1 spatial optical switches and optical memory. These time-division optical switches have conventionally been used, for example, in ``Time-division optical communication channel using bistable LD memory and waveguide type optical switch'' written by Keibe Kobayashi et al.
1988 IEICE General National Conference, Lecture No. 51
7-14. In these conventional technologies, a LiNb0a waveguide optical switch is used as an optical switch, an optical fiber delay line or a bistable semiconductor laser is used as an optical memory, and these are coupled through an optical fiber to form a time-division optical switch. There is.

[Problem to be solved by the invention]

The above conventional technology has a configuration in which two LiNb0a optical switches and an optical memory made of completely different materials are connected by an optical fiber. Due to the dependence of light on the polarization direction, a great deal of effort is required to adjust connections with other components.

There were problems such as: (1) coupling loss occurs at each connection point, so the insertion loss of the entire element becomes large; and (2) manufacturing cost increases.

An object of the present invention is to solve the above-mentioned problems and provide a time division optical switch that is small, does not require adjustment, has low insertion loss, and is inexpensive.

[Means to solve the problem]

The above object is achieved by constructing the spatial optical switch and the optical storage element (optical memory) using the same type of compound semiconductor material and integrating them on the same type of compound semiconductor substrate.

The outline of the present invention will be explained below using FIG. 1.

Here, for the sake of simplicity, the case where the number of channels: n=4 will be explained as an example. In the figure, the incident side leading waveguide 3 intersects with four optical waveguides 21 to 24, and optical switches 11 to 14 are arranged at each intersection point. The optical waveguides 21 to 24 communicate with the optical memories 31 to 34, and further intersect with the output side optical waveguide 4, and optical switches 15 to 18 are also arranged at the intersection points.

The optical signal incident on the input side optical waveguide 3 is sequentially transferred to the optical memories 31 to 34 by an optical switch drive signal synchronized with the optical signal.
will be written to. The written optical signal is read out to the output side optical waveguide 4 through the optical switches 15 to 18 by a readout signal according to a specified order. At this time, by arbitrarily changing the order of the read signals, the signal channels can be alternated on the time axis.

[Effect]

As shown in FIG. 1, according to the configuration of the present invention, the optical switch section and the optical memory are all connected by the same optical waveguide, so there is no need to make new connections between these elements, and there is no need to make new connections at the connection points. Loss can also be reduced. Furthermore, by constructing the optical switch section with an optical switch having no polarization direction dependence, such as a total reflection type, it is possible to obtain a time-division optical switch that has no polarization direction dependence as a whole and can be easily connected to an optical fiber.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 An optical integrated circuit as shown in FIG. 1 was fabricated on an n-InP substrate 1. The optical switch section is Y-shaped as shown in FIGS. 2 and 3, and a current injection section is provided in one part of the leading waveguide by Zn diffusion as shown at 56 in FIG. The refractive index is reduced by a current flowing through the laser beam, and the incident light is switched by total internal reflection. As shown in FIG. 4, the optical memory section used a distributed feedback bistable semiconductor laser having a tandem electrode structure with a non-injected region in the center.

The present optical integrated circuit was manufactured as follows.

First, distributed feedback 1j on the InP substrate! (DFB) A diffraction grating for a laser was formed by an interference exposure method. DF on top of that
B laser multilayer film layer was grown by liquid phase crystal growth (LPE) method. Next, the multilayer film in the switch region was etched, leaving the DFBL; After this, mesa etching is performed to form optical waveguides 3.4.21 to 28, Zn diffusion 56, 7a for current injection of the optical switch and DFB laser electrode contact is performed, and p-side electrodes 57, 83°8 are formed.
4 was deposited. Finally, the back surface was polished and etched to make it mirror-finished, and then the n-side electrodes 60 and 82 were deposited.

The device dimension of the 4-channel optical integrated circuit for time-division optical switching produced by this method was 6 m in length.

Single-mode optical fibers were connected to the input and output sides of this optical integrated circuit, and the transmission characteristics of optical signals were measured.

The optical signal used was a 32 Mb/S optical signal obtained by multiplexing 8 Mb/S digital signals into four channels and a pulse width of 15 ns. After this input optical signal is sequentially separated by the 1×4 writing optical switches shown in FIGS. 21 to 24, each bistable L
Sent to D. In response to this optical signal, the bistable LD drives 0 then 4×1 readout switches ]-5 to 18 in the order of 16.15 and 18.17, which hold one of the binary light quantities.

This procedure was repeated for each time throttle in turn. In addition, the memory contents of bistable I and D were reset by a reset current pulse for each time throttle. In this way, it was confirmed that the incident light pulse train shown at 41 in FIG. 1 was exchanged in time series on the output side as shown at 42. In addition, the insertion loss of this optical integrated circuit for time division optical switch is 14
It was dB.

As described above, according to this embodiment, the time-division optical switch, which was conventionally constructed by connecting 1×n and n×1 optical switches and optical memories to each other through optical fibers, can be integrated on a chip with a length of 6++n. This has the effect of reducing the insertion loss of the optical switch, which was about 22 to 25 dB, by about 10 dB.

Example 2 A time division optical switch integrated circuit was manufactured in the same manner as described in Example 1. However, the optical waveguide layer (2 in FIG. 3) of the optical switch portion was non-doped. When a voltage was applied to the optical switch section (FIGS. 11 to 18) of this optical integrated circuit and the characteristics were measured in the same manner as in Example 1, it was confirmed that the incident optical pulse train could be exchanged in time series. Furthermore, it has been confirmed that even if a 256 Mb/S digital signal multiplexed with 4 channels of 64 Mb/S signals is used as an incident signal, it is possible to optically exchange the input signal pulse train in the same way.According to this example, By using refractive index change due to applied voltage, a time-division optical switch capable of high-speed light exchange can be integrated on a 6 m long chip. This eliminates the need for connections between each component and enables time-division optical switching with low insertion loss. This has the effect that the switch can be easily obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to integrate time-division type optical switches, in which conventional components are interconnected by optical fibers, on the same substrate, making it possible to achieve small size and high integration. This has the advantage that there is no loss at the connection point, and there is no need for fine adjustments at the time of connection.

[Brief explanation of the drawing]

FIG. 1 is an overview of an embodiment of the present invention, FIG. 2 is an overview of the optical switch section, FIG. 3 is a sectional view taken along line AA' in FIG. 2, and FIG. 4 is an overview of the optical storage element. It is a diagram. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Optical waveguide layer, 3, 4.21-28
... Optical waveguide, 11-18... Optical switch, 31-
34... Optical storage element, 41... Incident light pulse train, 4
2... De's no r! ::1 43 To 7th HL - Rusk Nawate J No. 2-2 No. 3 f4 Znja 1- Arrival

Claims (1)

[Claims] 1. A 1×n optical switch having a function of distributing an optical signal input into one channel to n channels, and an optical signal input into n-phase channels into one channel. n × 1 optical switches having a multiplexing function are connected to each other via n optical storage elements, and all of these elements are composed of the same type of compound semiconductor crystal and are placed on the same type of compound semiconductor substrate. An optical integrated circuit characterized by being integrally integrated. 2. The optical integrated circuit according to claim 1, wherein the optical storage element is constituted by a bistable semiconductor laser. 3. The optical integrated circuit according to claim 1, wherein the switching characteristics of the optical switch do not depend on the polarization direction of incident light. 4. The optical integrated circuit according to claim 1, wherein the optical switch switches the optical path using a change in refractive index caused by an injected current. 5. The optical integrated circuit according to claim 1, wherein the optical switch switches the optical path using a change in refractive index caused by an applied voltage. 6. The optical integrated circuit according to claim 1, wherein either or both of the optical switch and the optical storage element have a multiple quantum well structure.