JPS60113214A - Fiber type optical switch - Google Patents

Abstract

PURPOSE:To obtain an optical switch which has low insertion loss and is connected easily to another optical fiber by using a fiber type directional coupler and a fiber type phase shifter. CONSTITUTION:Linear polarized light from a laser 8 is made incident after being made into a linear polarized wave parallel to the principal axis of a stressed type fiber through a half-wavelength plate 10. The incident light is split into two equally by a 3dB coupler 11 and guided to photodetectors 14 and 15 through a 3dB coupler 13. The difference between both optical paths of a Mach-Zehnder interferometer is not zero completely, so when a voltage is applied to a piezoelectric element 12, the output of a detector 14 is zero and the light is guided to the photodetector 15. The voltage applied to the piezoelectric element is varied until the output of the detector 15 is zero, and the light is detected by the detector 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical switch with a low insertion loss and a simple configuration, especially since the input and output ends are all composed of optical cores. This relates to a simple optical switch.

As a conventional single mode optical switch, LiNbO
Figure 1 shows a waveguide type Matsuzender interferometer formed by scattering Ti mirrors on three substrates.
N A Phased by Ramaswamy, R, D, 5tandley, 0ptical, Co
upler -Pair 5WitCh N(Be1l
, 5yst, Tech, Jour,, vo
l, 55, no, 6. pp.

767-775.1976).

This type of optical switch consists of two 8 dB combiners5.・7
1, and a phase shifter 6 for imparting a phase change of π to the light that enters from the optical waveguide input end 1 and propagates. The phase shifter 6 applies a voltage to the A/electrodes arranged on both sides of the optical waveguide, thereby causing a phase change in the light incident from the optical waveguide input end 1 by the optical effect.

Now, there is an intensity P at the input end 1 of the optical waveguide. It is assumed that when light is incident on the phase shifter 6 and no voltage is applied to the phase shifter 6, the output of the optical waveguide output end 8 is zero and the output of the optical waveguide output end 4 is P. At this time, when an appropriate voltage (a voltage that causes a phase change of π) is applied to the phase shifter 6, the output of the optical waveguide output end 8 becomes P1, and the output of the optical waveguide output end 4 becomes zero, and the switching of light becomes zero. It will be done.

However, connecting such optical waveguides and optical fibers requires a high-precision jig, and since the beam spot sizes of the optical waveguides and optical fibers are different, they inherently have the disadvantage of high connection loss. It is difficult to apply to communications.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks by using a fiber-type directional coupler and a fiber-type phase shifter to provide an optical switch that can be easily connected to other optical fibers and has a low insertion loss. It is about providing. The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, in which 8 is a laser and 9 is a laser.
10 is a rod wave plate, 11 and 113 are fiber type 8 dB couplers, 12 is a cylindrical piezoelectric element, and 14.15 is a photodetector. The optical fiber used in Fig. 2 is a stress-applied 7-eyeper fiber (Miya et al., [Method for manufacturing single mode optical fiber with internal stress birefringence], Japanese Patent Application No. 56-45.
No. 87), mode birefringence B = 4XlO (wavelength 1.8 μ
The bead length is 8.25 mm).

FIG. 8 shows the relationship between the applied voltage of a phase shifter in which this stress-applying type 7 eyeper is wound 20 times around a cylindrical piezoelectric element and the phase change of linearly polarized light. The half-wave voltage (voltage at which the phase change is πrad) is V. = 10 (V).

FIG. 4 is a cross-sectional view of the structure of fiber type 8 (iB coupler), which is made by heating and stretching the stress-applying fiber with its main axes parallel to each other.
awachi, B.S., Kawasaki, and
K.O.

)1i11, 愼Fabrication of S
ingle-polarizationSingle-
Mode-Fiber Couplers n, El
ectronLett,, vol, 1B, no
, 22. pp. 962-964.1982).

In FIG. 4, 16 is a core, 17 is a stress applying part, and 18 is a core.
is covered with cladding.

In FIG. 2, the linearly polarized light from the laser 8? 'A
The wave plate 10 converts the light into a linearly polarized wave parallel to the main axis of the stress-applying fiber and makes it incident. The incident light is 8t
It is divided 1:1 by the lB coupler 11, and again
The light is guided to photodetectors 14 and 15 via B coupler 1B.

Since the optical path difference between the two optical paths of the Matsuharzender interferometer is not completely zero, when voltages V and (V)' are applied to the piezoelectric element, the output of the detector 14 is zero, and the light is guided to the detector 154c. . Next, the voltage applied to the piezoelectric element is v2=v□+10
(V), the output of the detector 16 becomes zero and the light is switched to the detector 14. The insertion loss of the 8 dB coupler is less than 1 dB. Further, when a piezoelectric element is used as a phase shifter, the response speed is several m5ec.

Note that two cylindrical piezoelectric elements are wound around both optical fibers, so that the two piezoelectric elements have a phase of 180 degrees with respect to each other.
° Reduce the switch voltage by applying different voltages.

Alternatively, instead of a cylindrical piezoelectric element, it is possible to apply heat to one optical fiber between the directional couplers, use a temperature change switch, bend the fiber, or apply ultrasonic vibration to the optical fiber. An optical switch can also be realized by applying voltage.

As is clear from the above description, according to the present invention, it is possible to realize an optical switch entirely composed of optical fibers. Therefore, it has great advantages as an optical switch that can be easily connected to other optical fibers and has extremely low insertion loss.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional optical switch using a LiNbo a optical waveguide, Fig. 2 is an embodiment of the present invention, and Fig. 8 is a diagram showing the relationship between applied voltage and phase change of a cylindrical piezoelectric element. ,
FIG. 4 is a sectional view showing the structure of a fiber type 8 dB coupler. 1, 2... Optical waveguide input end, 8.4... Optical waveguide output end, 5.7... Directional coupler, 6... Phase shifter, 8
... Laser, 9... Lens, 10... Bar wave plate,
11.18...Fiber type directional coupler (8dB coupler), 12...Phase shifter using cylindrical piezoelectric element, 14
．． 15... Photodetector, 16... Core, 17... Stress applying part, 18... Clad.

Claims (1)

[Claims] L A fiber-type directional coupler in which two cores exist in parallel within a common cladding at an interval that causes optical coupling, and half of the light incident on one core is coupled to the other core. , two optical cores each having a single core in an independent cladding in which the separated incident light propagates completely independently (and a fiber equivalent to the fiber-type directional coupler that recombines the propagating light). A core-shaped optical switch comprising a directional coupler and a phase shifter provided in the middle of the optical fiber. 2. The fiber directional coupler is a polarization-maintaining fiber directional coupler. 2. A fiber-type optical switch according to claim 1, wherein the optical fiber is a polarization-maintaining fiber.