JPS6035716A - Driving circuit for photoswitch - Google Patents

Abstract

PURPOSE:To perform surely initial setting and driving of a photoswitch by providing a control circuit consisting of a transistor which detects the charging voltage of a capacitor and maintains the specified charging voltage, an operational amplifier, a reference voltage generator, etc. CONSTITUTION:A power source is turned on and detected and initial setting and driving are performed at the point of the time t2 when a source voltage is increased and attains 5V. The charging voltage of a capacitor C settles constant at 4V at the point of the time t1 before the point of the time t2 when the power source is turned on and detected. The substantial driving current is consequently supplied via a transistor Q1 to a coil L for driving a photoswitch in the initial setting and driving of the photoswitch.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a drive circuit for an optical switch that applies a magnetic field to switch the path of an optical signal.

Prior Art and Problems In optical submarine repeaters, reliability is improved by using a dual light emitting source configuration. In that case, an optical switch is provided to switch the driving of the current light emitting source and the backup light emitting source, and to switch the output optical signal to the optical transmission line. For example, FIG. 1 shows a block diagram of the main parts of an optical submarine repeater, in which reproduced data is input from an input terminal IN to a branch circuit 1, and a branch output is applied to a drive circuit 2.3. The drive circuits 2.3 are controlled by the switching control circuit 7 so that one of them is activated, and the output of the activated drive circuit causes the light emitting sources 4.3, such as semiconductor lasers and light emitting diodes, to be activated. 5 is driven. Also, switching control circuit 7
Controls the optical switch 6 via the optical switch drive circuit 8, and performs switching control so that the optical signal from the light emitting source driven by the drive circuit in the operating state is output from the output terminal OUT. An optical transmission line such as an optical fiber is connected to this output terminal OUT, and an optical signal is transmitted through the optical transmission line.

Figure 2 shows a conventional optical switch drive circuit, in which a power supply voltage (2) is divided by resistors R1 and R2 and applied to a capacitor (C). In this state, the current flows to the optical switch driving coil. In an optical switch, an optical waveguide is switched by applying a magnetic field, and the switched state of the optical waveguide is maintained even if the applied magnetic field is cut off. Such an optical switch is already well known. For example, an input light is separated into two polarization components by a prism provided with a polarization separation multilayer film, and each polarization component is split into yttrium iron as a magneto-optic crystal. This method utilizes the Faraday effect of the YIG thin film by passing the light through a garnet (Y I G) thin film, and outputting the light that has passed through the YIG thin film through a prism equipped with a polarization separation multilayer film. A magnetic field is applied through a magnetic material. The above-mentioned coil L is provided on this semi-hard magnetic material, and light switching is performed by exciting the coil L.

In optical submarine repeaters, power is supplied from the land terminal station, and when the power is turned on, the rated voltage is not applied suddenly, but as shown in Figure 3, the rated voltage is gradually applied to ■1. It is applied by rising to . In the repeater, when the voltage exceeds a predetermined voltage 72, it is determined that power is being supplied and the repeater is put into operation. In addition, when the power is turned on, the optical switch 6 is driven to the initial setting, and in that case, since the power supply detection voltage is lower than the voltage at the fixed position, the charging voltage of the capacitor C becomes even lower, and the capacitor C
It was difficult to sufficiently drive the optical switch driving coil with the charging voltage of .

Purpose of the Invention The purpose of the present invention is to maintain the charging voltage of a capacitor constant when the power supply voltage is above a predetermined value, so that the initial setting drive of an optical switch can be easily performed when the power is turned on. That is.

Structure of the Invention The present invention provides an optical switch drive circuit that uses electric charges charged in a capacitor as a drive current for an optical switch, and includes a control circuit that detects the charging voltage of the capacitor and keeps the charging voltage constant. Examples thereof will be described in detail below.

Embodiment of the Invention FIG. 4 shows a circuit diagram of a main part of an embodiment of the invention, and the same reference numerals as in FIG. 2 indicate the same parts. Power supply voltage +V is applied to capacitor C after being divided by resistor R3 and resistors R4 and R5. A series circuit of a transistor Q2 and a resistor R6 is connected in parallel with the resistors R4 and R5. The charging voltage of the capacitor C is divided by resistors R4 and R5 and inputted to a child terminal of an operational amplifier OPA, and a reference voltage from a reference voltage generation circuit VRG is inputted to one terminal via a resistor R8. Resistor R7 is connected between the operational amplifier 0PAO terminal and the output terminal, and when the voltage proportional to the charging voltage of capacitor C is higher than the reference voltage, transistor Q2 becomes conductive due to the output of operational amplifier OPA, and resistor R
The current flowing through capacitor C is increased to lower the voltage applied to capacitor C, thereby controlling the charging voltage of capacitor C to be constant.

Therefore, even if the power supply voltage +■ is close to the power-on detection voltage, the charging voltage of the capacitor C can be set to a predetermined value, and in the initial setting drive of the optical switch, the transistor Q
When the switch 1 is turned on, a sufficient drive current can be supplied to the optical switch drive coil.

FIG. 5 is a curve diagram showing the relationship between the increase in power supply voltage and the increase in capacitor charging voltage, where curve a is the charging voltage of the capacitor according to the embodiment of the present invention, and curve a is the charging voltage of the capacitor of the conventional example. , curve C show the characteristics of each increase in power supply voltage. In the conventional example shown in Fig. 2, the resistor R1 is 2Ω, the resistor R2 and 4 are Ω, the resistance of the coil L is 20Ω, the capacitor C is 20μF, and the power supply voltage +■
is the case of 6V, and in the embodiment of the present invention shown in FIG. , resistor R4 is IOKΩ, resistor R5 is IOKΩ, resistor R6 is 2
Ω, feedback resistor R7 to 300 Ω, resistor R8 to 5 Ω.
This is for the case where the reference voltage from the reference voltage generation circuit VRG is 2V.

The power supply voltage is increased, and at time t2 when the voltage reaches 5V, power-on detection is performed and initial setting drive is performed.At that time t2, in the conventional example, the charging voltage of capacitor C is 3,3■, it is not possible to supply a sufficient drive current to the optical switch drive coil L. However, according to the embodiment of the present invention, at the time t when power-on detection is performed.
Since the charging voltage of the capacitor C becomes constant at time t1 before t1, sufficient drive current is supplied to the optical switch driving coil L through the transistor Q1 in the initial setting drive of the optical switch. You will be able to do so.

Note that the reference voltage generation circuit VRG may be a reference voltage generation circuit using a Zener diode or the like, but it is also possible to use an integrated circuit reference voltage generation circuit.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention includes transistors Q2.
Operational amplifier OPA, reference voltage generation circuit VRG, resistor R6
Even if the power supply voltage +■ is in the process of rising to the rated value, as long as it is above the predetermined value, the charging voltage of the capacitor C is kept constant, so the optical switch cannot be driven. Since the current can be made large enough,
There is an advantage that the initial setting drive of an optical switch in an optical submarine repeater or the like can be performed reliably.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the main parts of an optical submarine repeater, Figure 2 is a conventional optical switch drive circuit, Figure 3 is an explanatory diagram of the voltage applied to the optical submarine repeater when the power is turned on, and Figure 4 is the main part of the optical submarine repeater. FIG. 5 is a curve diagram showing the relationship between the increase in power supply voltage and the increase in capacitor charging voltage by comparing the embodiment of the present invention and the conventional example. Ql, Q2 are transistors, +V is power supply voltage, R1-R
8 is a resistor, L is an optical switch driving coil, C is a capacitor, OPA is an operational amplifier, and VRG is a reference voltage generation circuit. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney Akira Aitani, 1 other person Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] An optical switch driving circuit that uses electric charge charged in a capacitor as a driving current for an optical switch, characterized in that the optical switch driving circuit is provided with a control circuit that detects the charging voltage of the capacitor and keeps the charging voltage constant. circuit.