JP3120835B2 - Optical switch control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical switch control circuit, and more particularly to a switch control circuit for optimizing the optical output of an optical switch.

[0002]

2. Description of the Related Art Conventionally, there has been known an optical output stabilizing circuit in which a negative feedback control means for controlling the intensity of output light is provided in an optical switch to stabilize an optical output. For example, JP
Japanese Patent Publication No. -11229 discloses an optical output stabilizing circuit as shown in FIG.

In the figure, reference numeral 14 denotes an optical switch SW, l
5 is an optical branch, and 16 is a control unit CNT. The optical switch 14 receives the input light Li from the input terminal, and switches and outputs the output lights L ₀₁ and L ₀₂ from the output terminal. Here, the switching operation of the output light can be performed such that only one of the output lights L ₀₁ and L ₀₂ is selectively and alternately output, or the output lights L ₀₁ and L ₀₂ are simultaneously output. Alternatively, it may be operated so as not to output simultaneously.

[0004] Control unit CNTl6 inputs the output light L _01, L ₀₂ detects the intensity ratio of the respective light intensity or both, and outputs a control signal d and the drive signal e based on the detection result. The control signal d and the drive signal e are used for light intensity control and switching control of the optical switch 14, respectively. That is, the amount of optical loss generated in the optical switch 14 is adjusted by the control signal d, and the switching of the optical output port of the optical switch 14 is controlled by the drive signal e. The control signal d is used for adjusting the amount of light loss and _stabilizing the light intensity ratio of the output lights L ₀₁ and L ₀₂ output from the optical switch 14.

FIG. 5 is a diagram showing the light output characteristics of a conventional light output stabilizing circuit and the control operation of the output lights L ₀₁ and L ₀₂ .

In the characteristics shown in FIG. 5, the minimum value side and the maximum value side of the light intensity are set to OFF and ON of the optical switch 14, respectively.
In the conventional optical output stabilizing circuit, negative feedback control is performed on the optical switch control voltage Vc so that the light intensity ratio becomes constant. As described above, the light output stabilizing circuit of the related art constitutes a feedback control circuit that adjusts the light intensity ratio between the two output lights L ₀₁ and L ₀₂ by the control signal d from the control unit CNT16 so as to keep the light intensity ratio constant. The light intensities of the lights L ₀₁ and L ₀₂ or the ratio of the light intensities of both are made constant.

[0007]

The light output stabilizing circuit of the prior art has an automatic control system so that the light intensity or intensity ratio output from the optical switch can be set to a predetermined value.

However, in such a stabilizing circuit, the light output OFF side does not always coincide with the minimum value of the light intensity.
The width of the light intensity between OFF and ON of the light output cannot be made sufficiently large. In a system such as an optical cross-connect system or an optical ADM ring system of a wavelength division multiplexing optical transmission system, it is more important to increase the extinction ratio in each device.

(Object of the Invention) An object of the present invention is to always control the extinction ratio of an optical switch to a maximum state.

[0010]

An optical switch control circuit according to the present invention is an optical switch control circuit for controlling an optical loss of a one-to-many optical switch by a control signal, wherein an AC signal is added to a negative feedback control signal. AC addition means for outputting a control signal, and optical output of each output port of the point-to-multipoint optical switch
Converting means for converting the signals into electric signals;
Select the off-port voltage signal from the input voltage signals.
A means for extracting the AC signal component from the output of the selector, a means for sampling and holding the AC signal component by a pulse signal synchronized with the AC signal, and a means for detecting a voltage, and the detected voltage being preset. Means for outputting the negative feedback control signal so as to take a value. Or an AC adding means for adding an AC signal to a negative feedback control signal and outputting the control signal, and each of a one-to-many optical switch
Conversion that converts the optical output of each output port into an electrical signal
Means and an off-port of the voltage signal output from the conversion means.
And a selector for selecting the voltage signal of the
Means for extracting the AC signal component from a force, means for multiplying the AC signal component by a signal synchronized with the AC signal or the AC signal, and an output of the means for multiplying the output signal having a preset value. Means for outputting the negative feedback control signal.

Further , the optical switch control circuit of the present invention comprises: a one-to-two optical switch capable of adjusting light loss by a control voltage;
Means for superimposing an AC signal of several kHz on the control voltage of the optical switch; means for converting two optical outputs of the optical switch into voltage signals, respectively ; A selector for selecting a voltage signal, and the selector
Means for extracting the AC signal component from the output of, and a means for sampling and holding the extracted AC signal component with a timing pulse having a specific phase in the same cycle as the AC signal of several kHz to detect a voltage, Means for applying negative feedback to the control voltage of the optical switch based on the detected voltage.

(Operation) For example, a low-frequency signal of about several kHz is weighed to a voltage for controlling the optical loss of the optical switch, and a control signal based on the phase and amplitude of the low-frequency signal component detected from the output light is output. By applying feedback to the voltage, the output light on the OFF side of the optical switch is controlled to be minimized.

[0013]

FIG. 1 is a block diagram showing an embodiment of an optical switch control circuit according to the present invention. In FIG. 1, 1 is an optical switch (SW), 2-1 and 2-2 are optical branches, and 3-1 and 3-2 are light receiving elements (PDs) that use an optical branch output from the output of the optical switch 1 as a current signal. ), 4-l, 4-
2 is a current-to-voltage converter (I /
Vconv), 5 is a selector (SEL), 6 is a selector control unit (SEL CNT), 7 is a band-pass filter (BP)
F), 8 are a sample-and-hold circuit (SH), 9 is a pulse generator (PG), 10 is a differential amplifier, 1 is a low-pass filter (LPF), and 12 is an oscillator (OS).
C) and 13 are voltage drive units (DRV).

FIG. 2 is a diagram showing characteristics of the light intensity at each output port of the optical switch 1 according to the present embodiment with respect to the optical switch control voltage from the voltage driver DRV13. As shown in the figure, the optical switch 1 has such characteristics that each output port exhibits a minimum (OFF) at a specific optical switch control voltage (optimum value) and increases (ON) on both sides.

Next, the operation of this embodiment will be described.

In FIG. 1, an oscillator 12 has a frequency of several kHz.
A signal having a frequency f ₀ of about oscillates. The signal voltage is superimposed on the control voltage, and a signal voltage having a frequency component of f ₀ is applied to the optical switch 1 as an optical switch control voltage via the voltage driver DRVI3.

The output light from each output port of the optical switch 1 is split by the optical branches 2-1 and 2-2, and the light is received by the light receiving element 3-.
The light signals are converted into current signals corresponding to the respective light intensities by 1, 3-2. The current signal is converted into a voltage signal by current-voltage conversion of the I / V converters 4-1 and 4-2, and the voltage is selected by the selector SE.
Input to L5. The selector SEL5 is controlled by the selector control unit SEL CNT6, and is a port (off port) for which the light output of the voltage signal is to be turned off (minimum).
Side voltage signal. The output of the selector 5, only the frequency components of f ₀ is extracted by the band-pass filter BPF 7.

FIG. 3 is a diagram showing a voltage signal waveform of the output of the selector 5. As can be seen from the characteristics of each output port of the optical switch 1 shown in FIG.
Since the optical switch control voltage is in the opposite direction depending on whether the optical output OFF point (point of the control voltage optimum value) is large or small, when the optical switch control voltage has an AC component, the DC component (control voltage) is the optical component. The phase of the AC signal component output from the band-pass filter BPF7 is inverted (changes by 180 °) depending on whether it is larger or smaller than the output OFF point. A waveform a in FIG. 3 shows a state of an AC signal component included in the output of the bandpass filter BPF7 according to the output voltage waveform of the oscillator l2. When the DC component of the optical switch control voltage coincides with the point where the optical output is turned off (point of the control voltage optimum value),
The AC signal component included in the output of the bandpass filter BPF7 has a substantially full-wave rectified waveform.

The sample and hold circuit 8 includes an oscillator 1
The sampling operation of the AC signal component is performed by the output pulse waveform c of the pulse generator PG9 generated in synchronization with the output signal of the second signal. That is, the pulse generator 9
The sample and hold the peak voltage of the waveform a is an AC signal component included in the output of the bandpass filter BPF7 a pulse waveform c of repetition frequency f ₀ generated from performing.

When the control voltage does not coincide with the value of the optical output OFF (optimum control voltage), the voltage signal from the sample-and-hold circuit 8 depends on whether it is larger or smaller than the above-mentioned value. The output voltage b corresponds to the upper or lower peak value of the phase, and if the control voltage matches the above value (control voltage optimum value), the peak value of the substantially full-wave rectified waveform of the AC signal (output voltage b (intermediate value of b). In addition,
The intermediate value becomes zero output by the differential amplifier.

The low-pass filter LPF 11 smoothes the voltage signal detected by the sample hold circuit 8 and outputs a DC component. The DC component becomes a negative feedback signal of the optical switch via the voltage driver 13. As a result, negative feedback control is performed in accordance with the direction and amount of deviation of the optical switch control voltage from the optimum point, and finally the low-pass filter LPF
Control is performed so that the voltage signal output from 11 becomes zero.

As described above, when the OFF-side port (off-port) of the optical switch 1 is controlled to the optimum value, the other port automatically becomes the ON optimum value as can be seen from the characteristics of FIG.

In the above embodiment, the configuration in which the negative feedback control is performed in a state where the optical output OFF side of the optical switch is selected has been described. However, this control is performed in a fixed switching state of the optical switch. Nothing is mandatory. That is, the present invention can be applied to a case where the optical switch is repeatedly performing a switching operation. In this case, for example, a voltage holding circuit is provided at the output section of the sample hold circuit, and when the port is switched to the optical output ON state, the output of the sample hold circuit immediately before the port is held, and the port is set to the optical output OFF state. The switching control of the sample and hold circuit, the selector, or the like can be adopted so that the negative feedback operation is performed only in the case. Although the present invention has been described with the embodiment using the one-to-two optical switch, the optical switch has a similar optical loss characteristic between the port with the optical output off and the port with the optical output on as shown in FIG. Is applicable to a 1: n optical switch (n: a natural number of 3 or more). Furthermore, an example has been described in which a sample and hold circuit using a pulse signal synchronized with an AC signal superimposed on the control signal is used as a means for outputting a negative feedback control signal. Since it is sufficient to detect and output the amplitude from the AC signal component obtained from the optical output of the port, this point is, for example, that the AC signal component or a signal synchronized with the AC signal component is multiplied by the AC signal component. Obviously, the control signal can be obtained in the same manner.

[0024]

The optical switch control circuit of the present invention performs the negative feedback control so that the light output when the light output is OFF becomes the minimum light intensity. Therefore, the maximum extinction ratio in the light intensity characteristics of the optical switch is obtained. It is possible to obtain

Further, according to the present invention, even if the characteristics of the optical switch change due to a change in the ambient temperature or the like, or a drift occurs in the optical switch control voltage or the like, the optical switch is changed before and after such a change or drift. It is possible to maintain stable optical switch characteristics without substantially changing the extinction ratio of the optical switch.

[0026]

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an optical switch control circuit of the present invention.

FIG. 2 is a diagram illustrating a characteristic example of the optical switch according to the embodiment;

FIG. 3 is a diagram illustrating signals of a negative feedback circuit according to the present embodiment.

FIG. 4 is a diagram showing a configuration of a conventional technique.

FIG. 5 is a diagram illustrating characteristics of an optical switch according to the related art.

[Explanation of symbols]

 1, 14 Optical switch 2-1, 2-2, 15 Optical branch 3-1, 3-2 Light receiving element 4-1, 4-2 Current-voltage converter 5 Selector 6 Selector control unit 7 Bandpass filter 8 Sample hold Circuit 9 Pulse generator 10 Differential amplifier 11 Low-pass filter 12 Oscillator 13 Drive circuit 16 Control unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-25819 (JP, A) JP-A-59-45423 (JP, A) JP-A-6-160931 (JP, A) JP-A-5-254 323245 (JP, A) JP-A-60-147716 (JP, A) JP-A-60-111229 (JP, A) JP-A-5-248992 (JP, A) JP-A-2-166425 (JP, A) JP-A-2-24635 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/31-1/313 G02F 1/01-1/035 H04Q 3/52 H04B 10 / 00-10/28 JICST file (JOIS) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. A pair optical switch control circuit for controlling the control signal to optical loss of the multi-optical switch, an AC adding means for outputting the control signal by adding the AC signal to the negative feedback control signal, one-to-many Optical output of each output port of optical switch
Conversion means for converting each of the
Selects the off-port voltage signal from the stage output voltage signal
A selector for extracting the AC signal component from the output of the selector; a unit for sampling and holding the AC signal component by a pulse signal synchronized with the AC signal to detect a voltage; Output means for outputting the negative feedback control signal so as to obtain the adjusted value. 2. A pair optical switch control circuit for controlling the control signal to optical loss of the multi-optical switch, an AC adding means for outputting the control signal by adding the AC signal to the negative feedback control signal, one-to-many Optical output of each output port of optical switch
Conversion means for converting each of the
Selects the off-port voltage signal from the stage output voltage signal
Selector, means for extracting the AC signal component from the output of the selector, means for multiplying the AC signal or a signal synchronized with the AC signal by the AC signal component, and Means for outputting the negative feedback control signal so as to have a set value. 3. A 1-to-2 optical switches that can modulate the light loss by the control voltage, means for superimposing an AC signal of several kHz to a control voltage of the optical switch, each voltage signal of two optical outputs of the optical switch And a selector for selecting a voltage signal on the light output off side of the voltage signal.
Means for extracting the AC signal component from the output of the selector, and detecting the voltage by sampling and holding the extracted AC signal component with a timing pulse having a specific phase at the same cycle as the AC signal of several kHz. An optical switch control circuit, comprising: means for performing negative feedback on a control voltage of the optical switch based on the detected voltage.