JPS58192017A - Optical switch - Google Patents

Abstract

PURPOSE:To remarkably reduce an insertion loss and also to make a titled switch small-sized, by constituting an optical switch by use of a liquid crystal as a light valve, and placing a plate-like lens train on the incident and emitting faces of light. CONSTITUTION:A liquid crystal 16 is placed between thin films 18, 18', and transparent electrodes 17, 19, substrate glass 15, 15' and polalizers 14, 14' are placed successively toward the outside on said thin films 18, 18', by which an optical switch medium 11 is formed. Light which is made incident from an optical fiber (a) is made to branch along branching circuits a1, a2 and a3, and forms a focus at a position of a fixed focal distance by a lens 10A formed on a glass plate 10. In case when no electric field is applied between the electrode 17 and 19 which place the liquid crystal 16 between them, light which transmits an analyzer 14' is extinguished. On the other hand, when an electric field is applied between the electrode 17 and 19, linear polarized light passes through the analyzer 14'. Subsequently, it is condensed onto the end face of a passing optical fiber 13. Accordingly, in this way, the insertion loss is reduced remarkably and also the switch can be made small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light valve type optical switch, and more particularly to a compact optical switch with low crosstalk. It had been. That is, here, I is a group of optical fibers for input, ko is a group of photodetectors that operate according to the signal coming from the signal processing system j, and 3 is a semiconductor that emits light according to the signal detected by the photodetector senko. Laser group, and reference is laser group J
A group of optical fibers that transmits light emitted from a These work as follows. When signal light enters from optical fiber a in the optical fiber group, this signal light is branched from optical fiber a into three optical fibers a, , a2゜a,
4 times. Each branched optical fiber a, ~a
, the light from the photodetector A, in the photodetector group λ.

The destination is read out in advance by the signal coming from the optical fiber a, and a voltage is applied to the photodetector M by the signal processing system j. As a result, the photodetectors M, - M5. B, ~B, I C1~C5
Of these, only the photodetector is in the operating state nK, in which a photocurrent flows, that is, in the on state.

As a result, laser LD1. LD7. Each drive system of LD, AMP, , MP2. AMP, of which laser L
Only the drive system AMP of D operates, and the laser LD emits light. Laser light emitted from laser LD is connected to each party fiber a coupled to each laser LD1 +LD, LD.
/, b/, and CF2 are coupled only to light 7 Aiper C'. That is, the optical fibers a and a' are optically connected between the input optical fiber group 1 and the output optical fiber group 1.

In such a configuration, the number of photodetectors in the photodetector group is mxnf! for the number l of input optical fibers and the number of output optical fibers n. Only l is required. Moreover, the optical signal undergoes a two-stage conversion process in which it is first converted into an electrical signal and then converted back into an optical signal. Therefore, there are drawbacks such as an expensive optical switch and a complicated processing process.

An object of the present invention is to provide an optical switch that eliminates these drawbacks.

To this end, in the present invention, a light valve is used instead of a photodetector to constitute an optical switch, and a flat lens array is used to increase the light incidence efficiency.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an example of the optical switch of the present invention, where IO and lθ' are nine flat glasses formed with lenses, 1lFi
A medium having an optical switching function is interposed between the flat glass 10 and the glass, and 12 is an input optical fiber a.

Input optical fibers such as b and C, /3 are output optical fibers a'
, b', C', etc. are output optical fibers.

FIG. 3 shows details of the D-D' cross section in FIG. 2.

In FIG. 3, IOM and IOA' are convex lenses formed on glass plates 10 and 70', respectively.

l is a polarizer, /#' is an analyzer, 15 and 15/ are glass substrates for liquid crystal, l≦ is a substance whose optical axis changes depending on an electric field, for example, an oriented liquid crystal, 17 is a transparent electrode, /l and /I' is a thin film for liquid crystal alignment as a surface treatment layer of liquid crystal/B, /9 is a Fi transparent IL pole. Thin film of liquid crystal 16/
Sandwiched with I and /I', these thin $ 12 and /I'
are coated with transparent electrodes 17 and 19, respectively, and on the outside of these electrodes 17 and 19 are substrate glass/3 and ls
A polarizer /l and an analyzer l' are placed on both sides of the substrate glasses t3 and tsl to form an optical switch medium //. X in the figure indicates the trajectory of the light beam.

The light incident from the optical fiber a is transmitted to the drum circuit a.

The drums are struck along C2, a, and K. The split light is focused at a position at a constant focal length from a lens 10AK formed on the glass plate 10 (this focal length is preferably located at the center of the liquid crystal /4).

The light that has passed through the glass substrate 10 from the lens 10 is turned into linearly polarized light by the polarizer T, and passes through the transparent electrode 17 and the thin film /1. Now, assuming that no electric field is applied between the electrodes 17 that sandwich the liquid crystal 16, the main axis of the linearly polarized light is rotated by the liquid crystal 16, so the main axis of the analyzer 41' is polarized. If it is arranged parallel to the main axis direction of the analyzer l#, the light that passes through the analyzer l' will be extinguished. On the other hand, when a voltage is applied between the electrodes 17 and n, the liquid crystal l≦ is oriented in the direction of the electric field.
pass The incident light is focused by the lens 10A to the focal position and then spread out, but since the output lens 10A is also formed, the light that has passed through the analyzer 1' is focused on the end face of the optical fiber 13. be illuminated.

In the present invention, the light incident from the optical fiber lλ is efficiently coupled to the output optical fiber 13 with low loss by the lenses 10 and lOA' formed on the flat plates 10 and 10'. Become.

Furthermore, depending on the presence or absence of electric charge, it is possible to turn the light on and off, that is, to perform a switching action.

In forming the above-mentioned planar lenses 10mm and iomm', effective methods include selectively diffusing ions into multi-component glass, or drilling holes in a quartz glass body and inserting and fixing rod lenses into the holes. be.

Alternatively, a flat lens with a transparent electrode formed on one side and a surface treatment layer formed on the opposite side may be used.
In this case, the polarizer may be provided in front of the flat lens. In this case, the thickness of the optical switch can be effectively reduced.

As explained above, in the present invention, if an optical switch is configured using a liquid crystal as a light valve and flat lens arrays are arranged on the light incident and exit surfaces, the insertion loss is extremely low and the size is small. can form an optical switch.

Further, according to the present invention, all parts can be constructed in a flat plate-like laminated form, so by arranging a large number of lenses on a flat glass plate, it is possible to easily realize a matrix type optical switch. In the switch, the light beam passes through the optical switch medium part as a beam focused by the convex lens of the lens plate, so there is little crosstalk between the optical switches, and therefore the optical switch of the present invention constitutes a matrix type switch. It is suitable for

[Brief explanation of the drawing]

FIG. 7 is a schematic diagram showing an example of a conventional optical switch, FIG. 1 is a perspective view showing an example of the optical switch of the present invention, and turtle j is a sectional view showing the structure of a part thereof in detail. /...Input optical fiber group, -...Photodetector group, 3
...Semiconductor laser group, D...Output optical fiber group, 10, 10...Glass plate, 10 tOA...
Flat lens, //... optical switch medium, /co...
Optical 7-iper for input, 13... optical fiber for output, /
Tei...polarizer, polarizer...analyzer, /j+/
j...substrate glass, /6...liquid crystal, /
7+/9...Transparent electrode, /11/1...Surface treatment layer, X...Light beam. Patent applicant: Nippon Telegraph and Telephone Public Corporation Figure 2 (-He-1-)

Claims (1)

[Scope of Claims] 1) A substance whose optical axis changes depending on an electric field is disposed between first and second transparent electrodes facing each other, a light incident IIK polarizer of the first transparent electrode is disposed, an optical switch section having an analyzer disposed on the light exit side of the electrode; a first glass plate disposed at the light entrance 11 of the first transparent electrode and on which a first lens is formed; a first glass plate arranged on the light exit side and formed with a second lens; a manual optical fiber that guides input light to the first glass plate; and an output optical fiber that receives output light from the second glass plate. an optical fiber, and determining whether or not the input light is extracted as the output light depending on whether or not an electric field is applied to the first and second transparent electrodes. . 2. In the optical switch according to claim 1,
An optical switch characterized in that the substance is liquid crystal.