JP2004117966A - Waveguide optical element having optical output control function and its optical output control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveguide optical element by which optical output control is possible without requiring a complicated mechanism such as a branching device and an optical signal and to provide its optical output control method. <P>SOLUTION: In the waveguide optical element having an optical output control function, a heater 4 is provided on an upper part of a core 6 and a temperature measurement member 8 is arranged on a lower part of the core 6. Optical output is controlled by feeding an electric signal from the temperature measurement member 8 back to a temperature control circuit of the heater 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a waveguide-type optical element for controlling the optical output by applying a temperature to a part of a core and utilizing a thermo-optic effect, and a method for controlling the optical output.
[0002]
[Prior art]
In recent years, the Internet has rapidly spread, and there is a need to further increase the transmission capacity of a communication network. At present, a DWDM (Dense Wavelength Division Multiplexing) system for multiplexing and transmitting a plurality of optical signals having different wavelengths onto one optical fiber has been put to practical use, and recently, a transmission capacity per optical fiber has been realized. Is said to be close to 1 Tbit / s.
[0003]
In such a large-capacity transmission system, the use of an optical amplifier is indispensable. However, since the optical amplifier has gain wavelength dependence, problems such as receiver saturation and deterioration of the S / N ratio have been pointed out. I have. As one of means for solving such a problem, a method of providing a variable optical attenuator in a transmission system and adjusting an optical signal level for each wavelength has been studied.
[0004]
The variable optical attenuator controls the optical output by changing the refractive index of the core by a thermo-optic effect by adding a temperature to a part of the core to adjust the input optical signal to a required level. (For example, see Patent Document 1). FIG. 4 shows a conventional light output control method.
[0005]
That is, conventionally, as shown in FIG. 4, a temperature adding mechanism, for example, a Cr thin film heater 41 is provided in a part of the core 40 of the Mach-Zehnder interference circuit, and an optical signal from the input port 42 is output from the output port 43 and branched. Input to the device 44. Most of the optical signal input to the branching device 44 is output as output light, but several percent is converted from the optical sensor 45 into an electric signal and fed back to the control circuit 46 of the temperature adding mechanism. At this time, the temperature is added by changing the voltage by the variable voltage adder 47 in order to change the refractive index of the core so as to obtain the target light output level, and the light output is controlled.
[0006]
[Patent Document 1]
JP-A-11-133364
[Problems to be solved by the invention]
By the way, the conventional techniques as described above have the following problems to be solved.
That is, in the conventional light output control method, a part of the output light is branched, monitored, converted into an electric signal, and fed back to the temperature control circuit to control the light output, but the branch for monitoring the output light is performed. There is a problem that a device and an optical sensor are required, and the apparatus becomes complicated.
[0008]
The present invention provides a waveguide-type optical element capable of controlling light output without requiring a complicated mechanism such as a branching device or an optical signal, and a method of controlling the light output.
[0009]
[Means for Solving the Problems]
The present invention employs the following configuration to solve the above points.
<Configuration 1>
In a waveguide type optical element for controlling light output by adding a temperature to a part of a core of a waveguide, a waveguide having a light output control function characterized in that a temperature measuring member is arranged near the core. Wave path type optical element.
[0010]
<Configuration 2>
2. The waveguide type optical element having an optical output control function according to Configuration 1, wherein the temperature measuring member is disposed below the core.
[0011]
<Configuration 3>
3. The waveguide type optical element having a light output control function according to Configuration 1 or 2, wherein the temperature measuring member is a temperature measuring resistor.
[0012]
<Configuration 4>
The waveguide type optical element having an optical output control function according to any one of Configurations 1 to 3, wherein the waveguide type optical element is a variable optical attenuator.
[0013]
<Configuration 5>
The waveguide-type optical device having an optical output control function according to any one of Configurations 1 to 3, wherein the waveguide-type optical device is an optical switch.
[0014]
<Configuration 6>
The waveguide having the optical output control function according to the configuration 4 or 5, wherein the waveguide type optical element is configured by combining a plurality of the same types of the variable optical attenuator and the optical switch or a combination of different types. Wave path type optical element.
[0015]
<Configuration 7>
In a light output control method for a waveguide-type optical element for controlling light output by adding a temperature to a part of a core of a waveguide, a signal from a temperature measuring member arranged in the vicinity of the core is added to a temperature of the core. Controlling the light output by changing the temperature applied to the core by feeding back the light to the core, and controlling the light output of the waveguide type optical element having the light output control function.
[0016]
<Configuration 8>
8. The optical output control method for a waveguide type optical element having an optical output control function according to Configuration 7, wherein the temperature measuring member is disposed below the core.
[0017]
<Configuration 9>
The optical output control method for a waveguide optical device having an optical output control function according to Configuration 7 or 8, wherein the waveguide optical device is a variable optical attenuator.
[0018]
<Configuration 10>
9. The optical output control method for a waveguide optical device having an optical output control function according to Configuration 7 or 8, wherein the waveguide optical device is an optical switch.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described using specific examples.
[0020]
FIG. 1 is a view schematically showing a variable optical attenuator which is a kind of the waveguide type optical element of the present invention. (A) is a plan view thereof, and (b) is a view of a cross section taken along the line AA ′ of (a) viewed from the input port side. In FIG. 1A, reference numeral 1 denotes a variable optical attenuator, which is a type of a waveguide type optical element using a Mach-Zehnder interferometer combined with a directional coupler, and receives an optical signal from an input port 2; The optical signal level output from the output port 3 passes through the Mach-Zehnder interferometer with a heater 4 attached to a part of the Mach-Zehnder interferometer to increase the temperature and change the refractive index of the core. The light is controlled by changing its phase.
[0021]
At this time, the variable optical attenuator 1 of the present invention has a waveguide structure including cores 6 and 6 and a clad 7 on an insulating substrate 5 made of silicon (Si) or the like as shown in FIG. On one core 6, for example, a Cr thin film heater 4 is mounted. The temperature is added by the heater 4 and the optical signal output from the output port 3 is controlled to a target level.
[0022]
Incidentally, in the present invention, the temperature measuring member 8 is disposed below the core on which the heater 4 is mounted. The place where the temperature measuring member is disposed may be near the core, and is not particularly limited as long as the temperature can be accurately measured. As the temperature measuring member 8, for example, a temperature sensor such as a platinum temperature measuring resistor whose electric resistance changes according to the temperature may be used. This makes it possible to directly measure the temperature near the core when the heater above the core is operated.
[0023]
At this time, the temperature near the core is measured by, for example, the resistance measuring device 9 as the electric resistance of the resistance thermometer, and the electric signal is fed back to the temperature control circuit 10. A signal from the temperature control circuit 10 is sent to a variable voltage adder 11 applied to the heater 4. In this way, the light output is controlled so as to attain the desired output level.
[0024]
In this case, if the relationship between the voltage to be applied to the heater 4 and the light output generated by the temperature is measured in advance from the temperature measured by the temperature measuring member 8, the resistance value from the temperature measuring resistor is measured and the electric signal is converted to the temperature. By feeding back to the control circuit, the light output can be controlled by changing the temperature of the heater 4.
[0025]
FIG. 1 shows an example of a variable optical attenuator using a 2 × 2 Mach-Zehnder interferometer. The present invention relates to a variable optical attenuator using a 1 × 1 Mach-Zehnder interferometer as shown in FIG. Also, as shown in FIG. 3, the present invention can be applied to a variable optical attenuator using a Y branch circuit. In FIG. 2 and FIG. 3, a circuit for feeding back an electric signal from the resistance temperature detector to the temperature control circuit is omitted.
[0026]
Further, in the present invention, when the optical output is controlled, the optical signal can be completely output or not output at all, so that the optical switch can be applied as an optical switch for turning ON and OFF the optical output.
[0027]
In the above-described embodiment, an example in which the variable optical attenuator and the optical switch are used independently is shown. However, these elements can be variously combined to form a multi-channel waveguide optical element. .
[0028]
【The invention's effect】
As described above, according to the present invention, the temperature measuring member is arranged near the core of the waveguide to directly measure the temperature in the vicinity of the core. This eliminates the need for branching or providing an optical sensor, so that it is possible to provide a waveguide type optical element having a light output control function with a simple structure and to provide a simple light output control method.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing another embodiment of the present invention.
FIG. 3 is a diagram showing still another embodiment of the present invention.
FIG. 4 is a diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Variable optical attenuator 2 Input port 3 Output port 4 Heater 5 Insulating substrate 6 Core 7 Clad 8 Temperature measuring member

Claims (10)

In a waveguide type optical element for controlling an optical output by adding a temperature to a part of a core of a waveguide, a waveguide having an optical output control function characterized in that a temperature measuring member is arranged near the core. Wave path type optical element. 2. The waveguide type optical element having an optical output control function according to claim 1, wherein the temperature measuring member is arranged below the core. 3. The waveguide type optical element having an optical output control function according to claim 1, wherein the temperature measuring member is a temperature measuring resistor. 4. The waveguide type optical device having an optical output control function according to claim 1, wherein said waveguide type optical device is a variable type optical attenuator. 4. The waveguide type optical device having an optical output control function according to claim 1, wherein the waveguide type optical device is an optical switch. 6. The optical output control function according to claim 4, wherein the waveguide type optical element is configured by combining a plurality of the same types of the variable optical attenuator and the optical switch or a combination of different types. Having a waveguide type optical element. In a light output control method for a waveguide-type optical element for controlling light output by adding a temperature to a part of a core of a waveguide, a signal from a temperature measuring member disposed in the vicinity of the core is added to a temperature of the core. And controlling the optical output by changing the temperature applied to the core by feeding back the optical output to the optical output device. The method according to claim 7, wherein the temperature measuring member is disposed below the core. 9. The optical output control method for a waveguide optical device having an optical output control function according to claim 7, wherein the waveguide optical device is a variable optical attenuator. 9. The optical output control method for a waveguide optical device having an optical output control function according to claim 7, wherein the waveguide optical device is an optical switch.

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