JP2002169109A - Optical path switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical path switching device which suppresses chatterings, occurring in an output waveform, when switching optical path at a high speed. SOLUTION: This optical path switching device is provided with a mechanical optical switch, which switches the optical path by impressing a signal voltage to an actuator and a control circuit which supplies the signal voltage to the optical switch, and therein the voltage at an elapse of T/2 from the standing-up of the signal is 2/3 VH less, with respect to the standing-up amplitude VH of the signal and signal width T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical optical path switching device, and more particularly, to a fiber-driven optical switch, a mirror-driven optical switch, and a MEMS.

[0002]

2. Description of the Related Art With the development of optical communication, optical fiber communication networks have long optical paths and complicated branches. In such an environment, applications for switching an optical path (transmission path) of an optical fiber between lines in an optical communication device or an optical transmission device are increasing, and many optical path switching devices and optical switches are used. Looking at the optical switch by the switching method, there is a method that changes the refractive index and phase of the optical path electrically or optically to switch the traveling direction of the light, and a method that mechanically moves and changes the optical path and advances the light. A mechanical type that switches directions has been developed. As a low-loss optical switch that does not change the wavelength distribution of an optical signal, the latter mechanical optical switch is promising. In terms of the number of branches of an optical switch, a 1 × 2 type optical switch that switches one movable optical fiber to two fixed optical fibers, a 1 × m type optical switch in which the end faces of a large number of optical fibers face each other, or n Xm-type optical switches and the like. The purpose of switching the optical path is, in addition to normal line switching, for fault recovery applications where a broken transmission path is switched to another unbroken path, and maintenance and inspection for switching the line of an optical communication network in a building or area. It is also used for applications or for changing the optical path in a measuring device.

A conventional optical switch is disclosed in, for example,
No. 85522. In this optical switch, two blocks (plugs) in which an optical fiber is positioned and fixed are brought together and connected, and one block (movable part) is moved in parallel with respect to the other block (fixed part) so that the fixed optical fiber is connected to the fixed optical fiber. This is an optical switch that switches an optical path between movable optical fibers. It has a guide pin, a hole for holding the guide pin, and a hole for sliding the guide pin inside for realizing precise parallel movement. In this configuration, the switching mechanism of the optical switch is disposed in an open container.
The block is translated by an actuator using electromagnetic force. As another mechanical type, an optical switch that switches an optical path by moving a bism or a reflection mirror is also used.
In addition, there is an application not only for transmitting an optical signal from a movable optical fiber to a fixed optical fiber, but also for transmitting an optical signal in the opposite direction. Therefore, the side that inputs an optical signal to the optical switch is called an input optical fiber, and the side that outputs an optical signal from the optical switch is called an output optical fiber. If both are included, they are collectively referred to as optical fibers.

[0004]

In the field of optical switches, there is a need to improve the transmission speed of optical signals.
It is necessary to improve the switching speed of an actuator using an electromagnet or a permanent magnet with a coil wound around a yoke. When the magnetic field for moving the movable member was increased by increasing the voltage applied to the coil, the switching speed of the movable portion was increased, and the switching time could be shorter than in the past. However, there has been a problem that noise occurs in the light output.
Although the movable part could be moved quickly by increasing the magnetic field, the movable part violently collided with the positioning member for stopping the movement of the movable part, causing vibration of the movable part. When the movable block vibrates due to the collision, the butting between the movable optical fiber and the fixed optical fiber shifts, and an optical signal leaks between the fibers. As a result, noise was generated in the light output. This is called chattering. Also, for an optical switch or MEMS that switches the optical path by changing the direction of the mirror or the arrangement of the reflection plate, the switching speed increases when the voltage applied to the driving device is increased, but chattering occurs. In any case, chattering can be prevented by reducing the applied voltage, but the switching speed of the movable part and the mirror becomes slow. Therefore, an object of the present invention is to provide an optical path switching device that can prevent chattering even if the optical path is switched at high speed.

[0005]

SUMMARY OF THE INVENTION An optical path switching device according to the present invention comprises a mechanical optical switch for switching an optical path by applying a signal voltage to an actuator, and a control circuit for supplying a signal voltage to the optical switch. In the apparatus, the signal voltage is such that a voltage when T / 2 has elapsed from a rise of the signal is not more than 2/3 times _VH with respect to a rise amplitude _VH and a signal width T of the signal. . Here, the signal width T refers to the time from when the signal rises to when the value of the signal voltage becomes zero V, or the time when the reduced amplitude becomes a constant value after the signal rises.

Another optical path switching device of the present invention is an optical path switching device including a mechanical optical switch that switches an optical path by applying a signal voltage to an actuator, and a control circuit that supplies a signal voltage to the optical switch. The signal voltage has a waveform whose amplitude decreases after the rise of the signal, and the signal voltage has a signal width of 0.5 ms or more and 20 ms or less.

Another optical path switching device of the present invention is an optical path switching device including a mechanical optical switch that switches an optical path by applying a signal voltage to an actuator, and a control circuit that supplies a signal voltage to the optical switch. The signal voltage applied to the actuator has a maximum rising amplitude, a waveform having a reduced amplitude after the rising, and reducing the amplitude of the signal voltage before the rising of the optical output waveform in the switched optical path. Features. When using a fiber-driven optical switch, it is preferable to reduce the signal voltage before the optical fiber reaches the switching position in order to prevent chattering.

The waveform of the above-mentioned signal voltage may be a rectangular wave whose amplitude is gradually reduced, a sawtooth wave, a waveform which sharply decreases after rising, a waveform which decreases stepwise, or the like. Even when switching is performed at high speed, the movable portion does not vibrate, and noise (chattering) of the output waveform can be suppressed.

In the present invention, it is preferable that the actuator is of a type driven by a magnetic field generated by a coil (an electromagnetic coil type). The optical switch applied to the present invention is a fiber-driven optical switch that switches an optical path by moving a movable section having a movable optical fiber with respect to a fixed section supporting a fixed optical fiber, wherein the actuator is a permanent switch. The movable portion may be moved by a magnetic field of a magnet and a magnetic field generated by a coil. When the magnetic field of the permanent magnet is used, the force attracted when the movable part approaches the stop position is large. Since the movable portion collides with the positioning member, the vibration increases and chattering easily occurs. Therefore, it is necessary to apply the configuration of the present invention.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a relationship between a driving signal voltage and light input / output of an optical path switching device according to an embodiment of the present invention. FIG. 1A shows an optical path switching device including a 1 × 2 optical switch and a signal generating circuit 9 connected to the electrode terminals 2a and 2b of the optical switch. The internal structure of this optical switch was the same as that of the optical switch shown in FIGS. The driving signal voltage applied to the optical switch from the signal generation circuit 9 and the input / output of the optical switch are shown in the timing chart of (1b). First, a state where a constant laser beam was input from the input optical fiber 3 was set. The light input is ON. Here, when a sawtooth pulse wave is input as a positive signal voltage from the signal generation circuit 9 to the electrodes 2a and 2b, the optical output 1 of the output side optical fiber 4a is turned on without chattering, and the output side optical fiber 4b The light output 2 was turned off. Conversely, when a sawtooth pulse wave is input as a negative signal voltage from the signal generation circuit 9 to the electrodes 2a and 2b, the light output 1 is turned off and the light output 2 is turned on without chattering.

FIG. 1C shows a signal voltage input from the signal generating circuit 9 to the optical switch. This waveform was a sawtooth pulse voltage having a rising voltage _VH = 5 V, a signal width T = 4 ms, and a voltage of 3 V at time T / 2. When this signal voltage is applied to the coil of the optical switch, the attractive force due to the coil magnetic field is reduced when the movable part approaches the tip of the yoke, that is, when the attractive force due to the permanent magnet magnetic field is increased. The movable part could be moved to the fiber connection position so as not to become too much.

FIG. 2 is a graph for explaining another waveform of a driving signal voltage. If the method or design of the actuator is changed, the rise voltage and the degree of amplitude reduction also change. In such a case, a signal generation circuit that outputs the waveform described in FIG. 2 can be used. For example, FIG.
a) is a signal voltage at which the rising voltage V _H = 7 V and the voltage sharply decreases after the rising. Signal width T is 5m
s, and the voltage at the end of the signal was 0.5 V. The voltage after a lapse of T / 2 from the rise was 2.8 V. FIG. 2 (2b)
Is a waveform having a rising voltage of 7 V, a signal width T of 5 ms, and a time T _O = 1.5 ms during which the amplitude changes stepwise.

In FIG. 2 (2c), the rising voltage is 5V, and the time T until the reduced amplitude becomes 1V is 2ms.
Time T corresponds to the signal width. After the time T, the voltage of 1 V was continuously applied until the next switching was performed. Fig. 2 (2d)
Is a waveform in which the amplitude decreases stepwise to a constant value of 0.5 V at a rising voltage of 5 V and a time T _O = 3 ms until the amplitude of the step changes. These signal voltages increase the rising amplitude to increase the movement (switching speed) of the movable part, and when the movable part starts to move, reduce the signal voltage sharply to reduce the force applied to the movable part and chatter. Was able to be suppressed.

FIG. 3 is a schematic view of another optical path switching device according to the present invention. The optical path switching device shown in FIG. 3A includes a signal generator 9b and an optical switch 1 having a waveform shaping circuit 5 built therein. After the rectangular wave output from between the terminals a and b of the signal generator is input from the electrodes 2a and 2b of the optical switch, the rectangular wave is connected by the waveform shaping circuit 5 connected between the electrodes.
The signal was shaped into a signal waveform as shown in (1c) and applied to the fiber drive circuit 6. As a result, the input side optical fiber 3 connected to the output side fiber 4a was switched to be connected to the output side fiber 4b. As another embodiment, as shown in FIG. 3 (3b), a configuration in which a waveform shaping circuit 5b for a series circuit is connected between the terminal a and the electrode 2a without incorporating a waveform shaping circuit between the electrodes 2a and 2b. It can also be used.

FIG. 4 shows the optical switch shown in FIG.
FIG. 1 is a perspective view illustrating an optical switch of a × 4 type, the appearance of which is described in detail. The fiber drive circuit and the like described below can be applied to the optical switch of FIG. FIG.
FIG. 5 is an exploded perspective view of the optical switch of FIG. In FIG. 4, the optical switch has a structure in which a ceramic housing 33 having a pair of electrodes 36 and optical switch switching means and the like, and a ceramic lid 35 provided with a pair of auxiliary electrodes 37 are provided. The input movable optical fiber 31 and the output fixed optical fiber 32 are fixed so as to protrude from the cutout provided in the housing 33. The housing 33 and the lid 35 were joined with an epoxy adhesive 34. The notch provided in the housing 33 was also closed with the adhesive 34 and sealed. Case 33 and lid 3
The sealed space of No. 5 was filled with an index matching agent. Dimensions excluding electrodes are 28mm long, 16mm wide, 8m high
m.

FIG. 5 shows a state in which the lid 35 is removed for easy explanation of the internal configuration of the optical switch. A state in which the lid 35 and the housing 33 are joined with an adhesive along the dotted line corresponds to FIG. 4 described above. This optical switch drives the optical fiber switching means by changing the direction of the current flowing through the electrode 36, thereby changing the combination of the input movable optical fiber 31 and the output fixed optical fiber 32 opposed to each other. The laser light (optical input 1) input from the input movable optical fiber 31 is guided to the output fixed optical fiber 32, and the optical path is switched to one. The recess 35 b provided on one side of the lid 35 corresponds to a pair of electrodes 36 provided on the housing 33. The recess 35b is provided to prevent the cover 35 from pressing the electrode 36 even when the cover 35 and the housing 33 are joined. A pair of auxiliary electrodes 37 are driven into the lid 35 at the other end of the lid 35. The auxiliary electrode 37 is used as a means for supplying a current when another electric circuit is assembled in the optical switch. FIG.
The direction of arrow X is parallel to the length direction of the optical fiber, the direction of arrow Y is substantially parallel to the direction in which the movable block moves, and the direction of arrow Z corresponds to the thickness direction of the optical switch.

The optical fiber switching means of the optical switch shown in FIG. 5 will be described in detail. The optical fiber switching means provided inside the housing 33 includes an input-side fixed block 41, a movable block 42, an output-side fixed block 43, and a fiber drive circuit 47 for moving the movable block 42 in the YY 'direction.
And a movable optical fiber 31 for inputting an optical signal and a fixed optical fiber 32 for outputting an optical signal. The two input movable optical fibers 31 are connected on the way to the input side fixed block 4.
1 and the tip is provided on the movable block 42.
The tips of the four output-side optical fibers 32 are provided in the output-side fixed block 43. The movable block 42 and the output-side fixed block 43 are each provided with an optical fiber 3
They faced together with the end faces 1 and 32. An optical signal (laser light) can be transmitted between the opposing optical fibers.

The fiber driving circuit 47 winds a coil 45 around a substantially U-shaped yoke 44, and the substantially U-shaped yoke 4
4, an output-side fixed block 43 and a permanent magnet 46 are arranged. A plus or minus switching signal voltage is applied to the coil 45 wound around each of the arms of the yoke 44 to move the movable block 42 in the Y or Y ′ direction between the tips of the yoke 44, The combination of the facing connection of the input optical fiber 31 and the output optical fiber 32 is changed. As a stopper for moving the movable block 42 in parallel, the movable block 42 is provided with two protruding non-magnetic carbide pins (not shown). The output side fixed block 43 has two wide holes for inserting the non-magnetic carbide pin. The parallel movement of the non-magnetic carbide pin inside the wide hole allows the movable block to move close to one end of the magnetic yoke with a gap left when it is moved in parallel. When the movable block is supported by the carbide pins, there is a small gap between the movable block and the yoke even at the position where the optical fiber is connected. This gap prevents the movable block and the yoke from being attracted.

As the movable block, a single crystal ferrite having dimensions of 3.2 mm in width, 2.5 mm in length and 2.0 mm in thickness was used. The length is parallel to the fiber. The length of the movable fiber from the movable block to the fixed block on the input side is 7 mm. The moving distance of the movable block is 0.25mm
And In order to make the description easier to understand, FIG.
The illustration of the coating covering the nonmagnetic carbide pin and the optical fibers 31 and 32 is omitted.

FIG. 6 is a graph showing the difference in optical output when signal voltages having different waveforms are input to the optical switch. The horizontal axis t of the graph represents time. FIG. 6A shows a comparative example. When a rectangular wave 20 having a signal width of 5 ms and a voltage of 5 V is applied between the coils of the optical switch, chattering occurs in the optical output 21 which is turned ON (fiber connected state). .
FIG. 6 (6b) shows an embodiment of the present invention, in which the signal width 5
When the signal voltage 22 whose amplitude suddenly decreases at a rising voltage of 7 V for ms is applied between the coils of the optical switch, an optical output 23 without chattering is obtained.

[0021]

The optical path switching apparatus of the present invention is an optical path switching apparatus including a mechanical optical switch for switching an optical path by applying a signal voltage to an actuator, and a control circuit for supplying a signal voltage to the optical switch. Since the signal voltage has a waveform whose amplitude decreases after the signal rises, chattering of the output waveform can be suppressed even when the optical switch is switched at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the relationship between signal voltage and optical input / output in an optical path switching device of the present invention.

FIG. 2 is a graph illustrating another signal voltage waveform.

FIG. 3 is a schematic diagram of an optical switch according to another embodiment of the present invention.

FIG. 4 is a perspective view illustrating an appearance of an optical switch according to the present invention.

FIG. 5 is an exploded perspective view of the optical switch of FIG.

FIG. 6 is a graph comparing the light output of the present invention with the conventional light output.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical switch, 2a, 2b electrode, 3 input side optical fiber, 4a 4b output side optical fiber, 5 waveform shaping circuit, 5b waveform shaping circuit, 6 fiber drive circuit, 9 signal generating circuit, 9b signal generating circuit, 20 rectangular wave, 21 Light output of comparative example, 22 signal voltage, 23
Light output, 31 movable optical fiber, 32 fixed optical fiber, 33 housing, 34 adhesive, 35 lid, 35b
Recess, 36 electrodes, 37 auxiliary electrodes, 41 input-side fixed block, 42 movable block, 43 output-side fixed block, 44 yoke, 45 coil, 46 permanent magnet,
47 Fiber drive circuit

Claims (5)

[Claims] 1. An optical path switching device comprising: a mechanical optical switch that switches an optical path by applying a signal voltage to an actuator; and a control circuit that supplies a signal voltage to the optical switch, wherein the signal voltage is a signal of a signal. Rise amplitude _VH and signal width T
Wherein the voltage when T / 2 has elapsed from the rise of the signal is 2/3 _VH or less. 2. An optical path switching device comprising: a mechanical optical switch that switches an optical path by applying a signal voltage to an actuator; and a control circuit that supplies a signal voltage to the optical switch, wherein the signal voltage is a rising edge of a signal. An optical path switching device having a waveform whose amplitude decreases later, wherein the signal width of the signal voltage is 0.5 ms or more and 20 ms or less. 3. An optical path switching device comprising: a mechanical optical switch that switches a light path by applying a signal voltage to an actuator; and a control circuit that supplies a signal voltage to the optical switch, wherein the signal voltage is applied to the actuator. Is
An optical path switching device, wherein a rising amplitude is a maximum value, the amplitude is reduced after rising, and the amplitude of the signal voltage is reduced before an optical output waveform rises in the switched optical path. 4. The optical path switching device according to claim 1, wherein the actuator is driven by a magnetic field generated by a coil. 5. The optical switch according to claim 1, wherein the optical switch is a fiber-driven optical switch that switches an optical path by moving a movable section having a movable optical fiber with respect to a fixed section supporting a fixed optical fiber. The optical path switching device according to claim 4, wherein the movable portion is moved by a magnetic field of a magnet and a magnetic field generated by a coil.