JPS6167839A - Driving circuit of optical switch - Google Patents

Abstract

PURPOSE:To suppress serge voltages, to prevent switching transistors from damage and to improve the reliability of a circuit by connecting diodes in parallel with coils. CONSTITUTION:Exciting currents having reversed directions to each other are alternately applied to coils 31, 32 respectively through switching TRs 41, 42 to be driven by switching signals respectively and a magnetic field applied to a magnetooptic effect material is switched to switch an optical path. In this case, the diodes 51, 52 are connected in parallel with the coils 31, 32 and serge voltages due to the self-induction of the coil 31 and mutual induction between the coils 31, 32 are respectively controlled, so that the TRs 41, 42 can be prevented from damage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in optical switch drive circuits that drive optical switches used for switching optical transmission lines and the like.

FIG. 2 (al is a schematic diagram of an example of an optical switch.

■ is a magnetic circuit using a semi-hard magnetic material with square hysteresis characteristics, 21 is a yttrium iron garnet 1-(Y
22 is a polarizing prism, 23 is a half-wave plate, and 31
and 32 are a first coil and a second coil constituted by a pair of conducting wires, Inl is the first input terminal, In2
is the second input terminal, Ot+L1 is the first output terminal,
Further, 0ut2 is a second output terminal.

For example, when an excitation current 1 (l) is applied to the coil 31, the magnetic circuit l is magnetized as shown in N and S, and at this time, the optical switch is magnetized as shown by the solid arrow in Fig. 2 (bl). Assuming that an optical path is formed, when the excitation current 1 (2) is applied to the coil 32, the magnetization direction of the magnetic circuit 1 is reversed.

An optical path as shown by the dotted arrow in the figure is formed in the switch section 2 .

By the way, optical switches have recently come to be used in transmission lines for optical submarine communications, and it goes without saying that particularly high reliability is required when used for such purposes. do not have.

[Conventional technology]

Figure 3 (al is a circuit diagram of a conventional example of an optical switch drive circuit; the same symbols as in Figure 2 refer to the same objects, and 4
Reference numeral 1 designates a first switching transistor connected in series to the DC type 4V via a coil 31, and 42 represents a second switching transistor connected in series to the DC power source 2 via the coil 32.

With this configuration, by alternately inputting switching signals to the bases of the first switching transistor 41 or the second switching transistor 42, the first coil 31 and the second coil 32 are excited, respectively. Current 1 (1) and exciting current I (2)
are applied alternately.

[Problem that the invention seeks to solve]

In the optical switch drive circuit having the above configuration, for example, when a switching signal is input to the base of the first switching transistor 41, the collector voltage Vcl of the first switching transistor 41 is as shown in FIG. 3(b). , and the collector voltage Vc2 of the second switching transistor 42 changes as illustrated in FIG.
A surge voltage is generated due to mutual induction between the coil 32 and the coil 32,
There is a problem that the switching transistor 41 or the switching transistor 42 may be damaged.

[Means for solving problems]

The optical switch drive circuit according to the present invention alternately applies excitation currents in opposite directions to each of two sets of coils constituted by a pair of conducting wires through two sets of switching transistors driven by a switching signal. In an optical switch drive circuit that switches the optical path by switching the magnetic field applied to the effect material, by providing a diode connected in parallel to each of the coils.

This is an attempt to solve the above problem.

[Effect]

That is, the coil 31 through self-induction and mutual induction.
and the surge voltage generated in the coil 32.

This is suppressed by a diode 51 and a diode 52, respectively.

〔Example〕

The gist of the present invention will be specifically explained below with reference to an embodiment shown in FIG.

FIG. 1 (ai is a circuit diagram showing the configuration of one embodiment of the present invention. In FIG. 2, the same symbols as in FIGS. 2 and 3 refer to the same objects, and 51 is in parallel with the coil 31;
and a diode connected in the forward direction from the switching transistor 41 to the power supply V.

Further, 52 is a diode connected in parallel to the coil 32 and in a forward direction from the switching transistor 42 to the power supply V.

According to the above configuration, surge voltages caused by self-induction of the coil 31 and mutual induction between the coil 31 and the coil 32 are respectively suppressed as illustrated in FIGS. Alternatively, damage to the switching transistor 42 can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, the surge voltage generated by self-induction or mutual induction in the coil is suppressed, and damage to the switching transistor is prevented.
This has the effect of improving the reliability of the optical switch drive circuit.

[Brief explanation of drawings]

FIG. 1(a) is a circuit diagram of one embodiment of the present invention. Figures 1 (bl and C) are explanatory diagrams of the same embodiment. Figure 2 is a schematic diagram of an optical switch. Figure 3 (a) is a circuit diagram of a conventional example. Figure 3 (b) and TCI are It is an explanatory diagram of the same conventional example. In the figure. 31 is a first coil, 32 is a second coil. 41 is a first switching transistor. 42 is a second switching transistor. 51 is a first diode, 52 is the second diode.

Claims (1)

[Claims] By alternately applying excitation currents in opposite directions to each of two sets of coils formed by a pair of conducting wires through two sets of switching transistors driven by a switching signal, and switching the magnetic field applied to the magneto-optic material. An optical switch drive circuit for switching an optical path, characterized in that the optical switch drive circuit includes a diode connected in parallel to each of the coils.