KR100298418B1 - variable optical attenuator using the thermooptic device - Google Patents

Abstract

A variable optical attenuator using a thermo-optic element having an asymmetric branched polymer waveguide, the optical modulator comprising an asymmetrical Y-shaped branched waveguide and a driving electrode for power application, and a main output for transmitting attenuation output from the optical modulator. A port, a monitor port for extracting and monitoring a part of the main output port, and a dummy drain port separated from the Y-shaped branch waveguide in a curved shape to remove some of the input optical power, thereby making the optical signal uneven for each wavelength. In order to reduce the intensity of the signal properly, the optical signal of each channel is always monitored and uniformized, thereby enabling long-distance optical transmission without error.

Description

Variable optical attenuator using the thermooptic device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wavelength division multiplexing optical communication systems, and more particularly, to a variable optical attenuator using a thermo-optical element having an asymmetric branched polymer waveguide.

Recently, a wavelength division multiplexed optical communication system has been actively developed and distributed to effectively transmit a variety of information.

In such an optical communication system, different information is stored in several light sources having different wavelengths, and then multiplexed and transmitted through one optical fiber.

The receiving end demultiplexes and separates the multiplexed signal, and then receives an optical signal for each wavelength.

On the other hand, in order to transmit an optical signal over a long distance, it is necessary to use an optical amplifier in the middle of transmission in consideration of the decrease in the optical signal.

In addition, an add / drop function is required such as distributing a part of the optical signal to another point during transmission and adding a signal at that point again.

1 is a diagram illustrating a schematic configuration of a general WDM add / drop multiplexer.

As shown in FIG. 1, when looking at the optical signal transmitted through the optical amplifier, the optical output of each wavelength is different because the gain of the optical amplifier and the characteristics of the demultiplexer vary depending on the wavelength.

If the transmission is multiplexed in such a state, transmission of the optical power of each wavelength is further intensified and ultimately the transmission is impossible because the signal characteristics are degraded.

Therefore, it is necessary to make the output of the optical signal for each wavelength uniform before optical amplification or in the middle of the entire system.

In general, the optical attenuator serves to reduce signals of different wavelengths based on the wavelength of the smallest optical signal.

Prior art optical attenuators include, for example, a device that mechanically moves an optical fiber using a motor, a device using a microelectromechanical system (MEMS) actuator, and a part of the optical fiber, and then, on the surface thereof. Devices coated with special materials, and Mach-Zehnder interferometric modulator devices using thermooptic effects on silica substrates are known.

However, mechanical optical attenuators and optical attenuators made by grinding optical fibers have a problem in that they are large in size and impossible to integrate with other optical elements.

In addition, the optical attenuator using the MEMS device and the silica device has a problem in that driving voltage and power are high.

Furthermore, the above existing devices have a problem in that the attenuation can not be adjusted by monitoring the attenuation output in real time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problem, and an object thereof is to provide a variable optical attenuator using a thermo-optic device capable of reducing the intensity of an optical signal as desired.

1 is a view schematically showing a configuration of a general wavelength division multiplexing system

2 is a view schematically showing the configuration of a variable optical attenuator using a thermo-optic device according to the present invention.

3 is a view showing the structure of the polymer optical device of FIG.

The variable optical attenuator using the thermo-optical device according to the present invention is characterized by an optical modulator comprising an asymmetrical Y-shaped branch waveguide and a driving electrode for power application, a main output port for transmitting the attenuation output from the optical modulator, It consists of a monitor port that extracts and monitors a part of the main output port, and a dummy drain port that separates a part of the input optical power in a curved form from the Y-shaped branch waveguide.

Another feature of the present invention is that in the Y-shaped branch waveguide, the widths of the branch waveguides are different from each other, wherein the wide waveguide is used as the main output port and the small waveguide is used as the dummy drain port.

The variable optical attenuator using the thermo-optical device according to the present invention having the above characteristics will be described with reference to the accompanying drawings.

First, the concept of the present invention implements a variable optical attenuator using a polymer optical waveguide optical element using a thermo-optic effect, thereby variably reducing the intensity of the optical signal by an electric signal and precisely controlling the light output in real time. To make it possible.

2 is a view schematically showing a variable light attenuator using a thermo-optic device according to the present invention, and FIG. 3 is a view showing the thermo-optic polymer optical device of FIG. 2.

As shown in Figs. 2 and 3, the device extracts an optical modulator that can change the intensity of the optical signal using a thermo-optic effect, a main output port for transmitting the attenuation output, and a portion of the main output port. Monitor port to monitor.

First, the optical modulator is composed of an asymmetrical Y-shaped branch waveguide and an electrode for applying electric power.

Here, the two arms of the branch waveguide are different in width, and a large arm is used as the main output port.

The narrow arm is combined with a tapered S-shaped bend waveguide to pass and remove optical power that is attenuated from the input optical power to the output stage.

On the other hand, the wide arm used as the main output port to form a branched waveguide structure by properly connecting the curved waveguide to implement a monitor port that can extract a portion of the attenuated output optical signal.

Looking at the basic operating principle of the optical attenuator according to the present invention configured as described above are as follows.

First, in a state in which no power is applied to the electrode, the optical power input through the linear optical waveguide is mostly coupled to the wide arm by a modal evolution effect, and a part of the optical power is output to the monitor port.

On the other hand, when power is applied to the electrode, the effective refractive index of the wide arm is reduced due to the thermo-optic effect, so that a part of the input optical power is transferred to the narrow arm.

Therefore, the light intensity of the main output stage gradually decreases according to the applied power.

In general, the optical device varies in performance depending on the polarization state of the light. However, in the proposed optical device, the output of the monitor port is fed back to the electric driver to actively control the attenuation, so that even when the polarization or power of the input light changes, It can be used as an optical power regulator to produce a light output.

As described above, the present invention consists of an optical power tap largely formed of an asymmetric linear branched optical waveguide, a driving electrode, and a curved optical waveguide, and an optical power tap formed by appropriately coupling the curved waveguide to the main output port. By using the monitor port, the main output signal can be indirectly monitored in real time.

In addition, this signal is fed back to the power driver so that a constant light output can be obtained regardless of external changes such as polarization change of light, and the optical signal to be attenuated disappears from the branch other than the main output port of the branch. Effective removal through the arm.

In addition, since the intensity of the output optical signal is always maximized in the initial state in which no electric signal is applied from the outside, there is an advantage of not requiring an electric biaser, and since the operation is performed by a mode evolution effect, Compared to devices using interference phenomena, wavelength uniformity is excellent and fabrication tolerance is large.

As described above, the present invention relates to an optical attenuator capable of appropriately reducing the intensity of an uneven optical signal according to each wavelength in a wavelength division multiplexing optical communication system. There is an effect that makes it possible.

Claims (5)

An optical modulator comprising an asymmetrical Y-shaped branch waveguide and a driving electrode for power application; A main output port for transmitting an attenuation output from the optical modulator; A monitor port for extracting and monitoring a portion of the main output port; The variable optical attenuator using a thermo-optic device, characterized in that the dummy drain port is separated in a curved form in the Y-shaped branch waveguide to remove a portion of the input optical power. The variable optical attenuator using a thermo-optical device according to claim 1, wherein in the Y-shaped branch waveguide, widths of the branch waveguides are different from each other. 3. The variable optical attenuator using a thermo-optical device according to claim 2, wherein the wider waveguide is used as the main output port and the smaller waveguide is used as the dummy drain port. The variable light attenuator of claim 1, wherein the dummy drain port has an S shape. The variable light attenuator of claim 1, wherein the monitor port is curvedly connected to the waveguide which is the main output port.