JP2002062443A - Optical wavelength multiplexer/demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical wavelength multiplexer/demultiplexer wherein light output is uniformized, a satisfactory signal/noise ratio is obtained even after passing through a multistage optical fiber amplifier and signal extinction is prevented. SOLUTION: In the optical wavelength multiplexer/demultiplexer wherein a plurality of input waveguides 2 which input a wavelength division multiplex optical signal, an output waveguide 3 which multiplexes and outputs the wavelength division multiplex optical signal, an array waveguide 5 consisting of a plurality of waveguides having the prescribed difference ΔL of a waveguide length, an input side slab waveguide 4 which connects the input waveguides 2 to the array waveguide 5 and an output side slab waveguide 12 which connects the output waveguide 3 to the array waveguide 5 are provided on a substrate 1, variable light attenuators 6 are formed in the input waveguides 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength multiplexer / demultiplexer used in the field of optical communication, and more particularly to an arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer used in a wavelength division multiplex transmission system. It is about.

[0002]

2. Description of the Related Art In the field of optical communication, a method (wavelength division multiplexing) in which a plurality of signals are put on lights of different wavelengths and transmitted through one optical fiber to increase the information capacity has been put to practical use. I have. When transmitting signals using this wavelength division multiplexing method, especially in a system that performs long-distance transmission or wavelength add / drop, an optical fiber amplifier that amplifies an attenuated optical signal every tens of kilometers or for each add / drop station is installed. Have been.

As an optical wavelength multiplexer / demultiplexer for multiplexing or demultiplexing light of dozens of different wavelengths, an arrayed waveguide diffraction grating type is widely used.

FIG. 6 shows a conventional arrayed waveguide diffraction grating type element. The element 20 includes a plurality of input waveguides 2 for inputting a wavelength division multiplexed optical signal, an output waveguide 3 for multiplexing and outputting the wavelength division multiplexed optical signal, and a predetermined waveguide length on a substrate 1. An array waveguide 5 composed of a plurality of waveguides having a difference ΔL, an input slab waveguide 4 connecting the input waveguide 2 and the array waveguide 5, an output waveguide 3, and the array waveguide 5; And an output-side slab waveguide 12 for connecting the two.

The arrayed waveguide grating type optical wavelength multiplexer / demultiplexer can be manufactured by the same process and the same number of steps regardless of the number of channels. There is no deterioration. Therefore, this arrayed waveguide grating optical wavelength multiplexer / demultiplexer is easily regarded as a key device for wavelength division multiplexing transmission because it can easily cope with a case where the number of channels is increased.

With the explosive increase in the amount of information in recent years, there is an urgent need to increase the capacity of communication lines. Therefore, the number of wavelengths has been further increased. However, in order to increase the number of wavelengths, it is necessary to widen the wavelength band to be used.

[0007]

However, the above-mentioned optical fiber amplifier cannot always obtain a flat gain, and in order to widen the operating band, it is necessary to use an uneven band of the optical fiber amplifier. Often not.

[0008] An uneven gain such as a ripple causes an extreme difference in optical power depending on a signal (wavelength) due to a superposition of ripples in a long distance transmission or an add-drop system in which optical fiber amplifiers are connected in multiple stages. In such a case, there is a problem that light of a certain signal disappears.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to make the optical output uniform, to obtain a sufficient signal / noise ratio even after passing through a multi-stage optical fiber amplifier, and to prevent signal disappearance. It is to provide an optical wavelength multiplexer / demultiplexer which can be used.

[0010]

According to the first aspect of the present invention,
On a substrate, a plurality of input waveguides for inputting a wavelength division multiplexed optical signal, an output waveguide for multiplexing and outputting the wavelength division multiplexed optical signal, and a plurality of output waveguides having a predetermined waveguide length difference ΔL. An array waveguide composed of a waveguide, an input slab waveguide connecting the input waveguide and the array waveguide, and an output slab waveguide connecting the output waveguide and the array waveguide. In the optical wavelength multiplexer / demultiplexer, an optical variable attenuator is formed in the input waveguide.

According to a second aspect of the present invention, in the first aspect, a function of monitoring an optical output of the variable optical attenuator is provided.

According to a third aspect of the present invention, in the second aspect, the function of monitoring the optical output of the optical variable attenuator is constituted by a waveguide formed on the substrate. It is arranged between the optical variable attenuator and the input side slab waveguide, and is connected to the input waveguide or the optical variable attenuator.

The invention described in claim 4 is the first to third aspects of the present invention.
5. The optical variable attenuator according to claim 1, wherein at least one heater is formed on the variable optical attenuator, and the temperature of the variable optical attenuator is adjusted by the heater. A function of obtaining the amount of light attenuation.

According to a fifth aspect of the present invention, in accordance with the fourth aspect, the temperature of the variable optical attenuator is adjusted based on the optical output detected by the function of monitoring the optical output of the variable optical attenuator. The function is provided.

[0015]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1A, reference numeral 20 denotes an arrayed waveguide diffraction grating type element. The element 20 includes, on a substrate 1, a plurality of input waveguides 2 for inputting a wavelength division multiplexed optical signal, an output waveguide 3 for multiplexing and outputting the wavelength division multiplexed optical signal,
An array waveguide 5 composed of a plurality of waveguides having a predetermined waveguide length difference ΔL, an input slab waveguide 4 connecting the input waveguide 2 and the array waveguide 5, an output waveguide 3 and an array An output side slab waveguide 12 for connecting the waveguide 5 is provided.

As shown in FIG. 1B, a variable optical attenuator 6 is formed in each of the input waveguides 2, and the variable optical attenuator 6 has approximately 1% of the light transmitted through the variable optical attenuator 6. % Is formed.

The optical tap monitor waveguide 7 has a function of monitoring the optical output of the variable optical attenuator 6. The waveguide 7 is arranged between the variable optical attenuator 6 and the input side slab waveguide 4 and is connected to the input waveguide 2. This monitor waveguide 7 may be connected to the variable optical attenuator 6.

In the present embodiment, the optical circuit of the element 20 is formed by photolithography and etching, as in the conventional manufacturing method.

As shown in FIG. 2, the element 20 is formed on a substrate 1 by a buffer layer 8 and a core layer 1 by flame deposition and sintering.
0 and a cladding layer 9 are sequentially provided, and an arrayed waveguide type diffraction grating, a variable optical attenuator 6, and a monitor waveguide 7 are formed on a photomask. An electrode (not shown) and a heater 11 are formed. This waveguide manufacturing method has the same number of steps as the conventional manufacturing method.

Note that a glass substrate, a semiconductor substrate, a resin-based substrate, or the like is used as the substrate 1, and a core layer, a clad layer,
It is desirable that an optically transparent material such as a glass-based material or a semiconductor material be used for the buffer layer.

Next, the operation of this embodiment will be described.

Light having a wavelength assigned to each port and entering the input waveguide 2 is guided to the variable optical attenuator 6.
In the variable optical attenuator 6, when the heater 11 is energized,
The temperature rises and the proportion of transmitted light is adjusted by the thermo-optic effect of the glass.

The light transmitted through the variable optical attenuator 6 is partially guided to the monitor waveguide 7, and the rest is guided to the input waveguide 2 as a transmission signal. The light is multiplexed with the light having the wavelength and propagated to the output waveguide 3.

In this embodiment, on the variable optical attenuator 6,
As described above, at least one heater 11 is formed. Therefore, the temperature of the variable optical attenuator 6 can be adjusted by controlling the amount of current supplied to the heater 11, the current supply time, and the like. Thus, a desired amount of light attenuation in the variable optical attenuator 6 can be obtained. The temperature adjustment of the variable optical attenuator 6 is desirably performed based on the optical output detected by the function of monitoring the optical output of the variable optical attenuator 6.

When transmitting a signal by the wavelength division multiplexing method,
In particular, in a system that performs long-distance transmission or wavelength add / drop, an optical fiber amplifier that amplifies an attenuated optical signal is installed every several tens of kilometers or for each add / drop station.

In this embodiment, by setting the attenuation of each wavelength in the optical variable attenuator 6 so as to cancel the gain characteristic (for example, see FIG. 3) of the optical fiber amplifier used in this system, Even after passing through the fiber amplifier, it is possible to perform signal transmission that is uniform and does not cause signal disappearance.

In this embodiment, the power of the light propagating to the monitor waveguide 7 is sequentially monitored and fed back. Then, the heating temperature of the heater 11 is adjusted, whereby the attenuation of the variable optical attenuator 6 is adjusted.

FIGS. 4 and 5 show the loss wavelength characteristics of the optical wavelength multiplexer / demultiplexer having the optical variable attenuator 6. FIG. FIG. 4 shows the loss wavelength characteristic when the attenuation of the variable optical attenuator 6 is set to zero (when the heater is off). FIG. 5 shows some of the ports (for example, Ports 11 and 2
11 shows the loss wavelength characteristics when the signal is attenuated by 10 dB for (0). By adjusting the heating amount of the heater 11 for each port, an arbitrary light output can be obtained at each wavelength.

The variable optical attenuator 6 is not affected by a change in environmental temperature or the like because the amount of attenuation is adjusted by the heater heating temperature.

[0031]

According to the present invention, the deterioration of the signal / noise ratio, which is affected by the gain characteristics of the optical fiber amplifier used in the system, can be reduced, and the wavelength multiplexing system, particularly, the optical fiber amplifier is connected in multiple stages. Devices that are effective for long-distance transmission and add-drop systems.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer according to the present invention, in which (a) shows an optical wavelength multiplexer / demultiplexer in which a variable optical attenuator and a monitor waveguide are arranged. (B) is a partially enlarged view of FIG.

FIG. 2 is a sectional view taken along the line II-II of FIG. 1 (b).

FIG. 3 is a diagram illustrating an example of a gain characteristic of an optical fiber amplifier.

FIG. 4 is a diagram illustrating a loss wavelength characteristic when the optical variable attenuator is powered off.

FIG. 5 is a diagram illustrating a loss wavelength characteristic when a part of ports of the input waveguide is attenuated by 10 dB.

FIG. 6 is a plan view showing a conventional arrayed waveguide grating optical wavelength multiplexer / demultiplexer.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 input waveguide 3 output waveguide 4, 12 slab waveguide 5 array waveguide 6 variable optical attenuator 7 monitor waveguide 8 buffer layer 9 clad layer 10 core layer 11 heater 20 array waveguide diffraction grating type element

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichinori Tamura 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Within the Opto-System Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Naoto Uezuka Hitachi, Hitachi 5-1-1 Takamachi Hitachi Cable, Ltd. Optro System Laboratory F-term (reference) 2H047 KA03 KA12 LA19 MA05 RA08 TA11 2H079 AA06 AA12 BA01 CA04 EA05 EB27 HA11 KA20

Claims (5)

[Claims] 1. A plurality of input waveguides for inputting a wavelength division multiplexed optical signal, an output waveguide for multiplexing and outputting the wavelength division multiplexed optical signal, and a predetermined waveguide length difference ΔL on a substrate. An arrayed waveguide including a plurality of waveguides, an input side slab waveguide connecting the input waveguide and the arrayed waveguide, and an output side slab connecting the output waveguide and the arrayed waveguide. An optical wavelength multiplexer / demultiplexer, comprising: a waveguide; and an optical variable attenuator formed in the input waveguide. 2. The optical wavelength multiplexer / demultiplexer according to claim 1, further comprising a function of monitoring an optical output of said variable optical attenuator. 3. The function of monitoring the optical output of the variable optical attenuator comprises a waveguide formed on the substrate.
3. The waveguide according to claim 2, wherein the waveguide is disposed between the optical variable attenuator and the input side slab waveguide, and is connected to the input waveguide or the optical variable attenuator.
An optical wavelength multiplexer / demultiplexer according to any of the preceding claims. 4. At least one heater is formed on the variable optical attenuator, and the heater adjusts the temperature of the variable optical attenuator so that a desired amount of optical attenuation in the variable optical attenuator can be reduced. The optical wavelength multiplexer / demultiplexer according to any one of claims 1 to 3, further comprising a function of obtaining the wavelength. 5. The apparatus according to claim 4, further comprising a function of adjusting the temperature of said variable optical attenuator based on the optical output detected by the function of monitoring the optical output of said variable optical attenuator. Optical wavelength multiplexer / demultiplexer.