JP2001141944A - Optical wavelength multiplexer / demultiplexer - Google Patents

Abstract

(57) [Problem] To provide a low crosstalk optical wavelength multiplexer / demultiplexer that can achieve flattening over a wide band, can set the center wavelength with high accuracy, and can achieve low crosstalk. SOLUTION: A band adjusting waveguide element 11 is provided between an input optical fiber 2 and an input side slab waveguide 10, and a position and a shape of the band adjusting waveguide element 11 are optimized to widen a band. And other waveform adjustments. By arranging additional waveguides 7a and 13a on the band adjustment waveguide element 11 and the output side waveguide 7, respectively,
Even if a slight axis shift occurs when these elements are fixed, the center wavelength can be accurately set by combining the waveguides.

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. 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 light of different wavelengths and transmitted through one optical fiber to increase the information capacity has been put to practical use. . In this method, a multiplexer / demultiplexer that multiplexes or demultiplexes light having different wavelengths plays an important role.

In particular, an arrayed waveguide type diffraction grating can be manufactured by the same process and the same number of steps regardless of the number of channels, and there is no characteristic deterioration such as an increase in loss in principle. In this case, it is considered promising as a key device for wavelength multiplex transmission.

FIG. 5 is a plan view showing a conventional example of a wavelength multiplexer / demultiplexer.

The wavelength multiplexer / demultiplexer shown in FIG. 1 includes a substrate 1, an input-side slab waveguide 3 formed on the substrate 1, for inputting a wavelength division multiplexed optical signal from an input optical fiber 2a, and an input-side slab waveguide. An arrayed waveguide 4 which is connected to the waveguide 3 and has a plurality of waveguides 4a having a predetermined waveguide length difference ΔL, and which demultiplexes the wavelength division multiplexed optical signal input to the input optical fiber 2a.
And an output slab waveguide 5 connected to the array waveguide 4
And a plurality of output waveguides 7 connected to the output slab waveguide 5 and outputting the demultiplexed optical signals to the output optical fiber 6, respectively.

The transmission wavelength of this wavelength multiplexer / demultiplexer is 0.8 nm (about 100 GHz) according to the international standard.
In general, the channel interval and the transmission center wavelength are set by the above or a multiple thereof.

Here, in the case of using an arrayed waveguide type diffraction grating, for example, when quartz is used, it has a temperature coefficient of about 0.01 nm / .degree.
A method of keeping the temperature of the optical element constant and fixing the transmission wavelength is adopted.

However, in the active control system in which the center wavelength is set by using a heater or a Peltier element, power supply is required, and the cost is high.

In recent years, studies have been made on a temperature-independent array waveguide diffraction grating type optical multiplexer / demultiplexer (Inoue et al.,
1998 IEICE General Conference C-3-117). In this method, a groove is formed in the arrayed waveguide portion by etching, and a resin having a temperature coefficient opposite to that of quartz glass is inserted into the groove to make the transmission wavelength independent of temperature. In this method, since the waveguide is temperature-independent, fine adjustment of the center wavelength setting using a heater or a Peltier element, which has been conventionally performed, cannot be performed.

For this reason, a system has been adopted in which the single-core optical fiber is directly connected to the end face of the slab waveguide, and the center wavelength is controlled by adjusting the bonding position of the fiber.

[0011]

However, when an optical fiber is directly connected to an end face of a slab waveguide, a Y-branch structure, a parabolic horn structure, or a tapered waveguide is introduced before the slab waveguide conventionally used. Thus, there has been a problem that it is not possible to take a method of optimizing the electric field distribution and achieving broadband / flattening or low crosstalk. In addition, in order to accurately set the center wavelength, there is a problem that when the optical fiber is fixed to the end face of the slab waveguide, it is necessary to shift the axis within a range of sub μm to several μm.

Accordingly, an object of the present invention is to provide an optical wavelength multiplexer / demultiplexer which solves the above-mentioned problems, can achieve flattening in a wide band, can accurately set a center wavelength, and has low crosstalk. It is in.

[0013]

In order to achieve the above object, an optical wavelength multiplexer / demultiplexer according to the present invention comprises a substrate and an input side for receiving a wavelength division multiplexed optical signal from an input optical fiber formed on the substrate. A slab waveguide, an arrayed waveguide connected to the input side slab waveguide and comprising a plurality of waveguides having a predetermined waveguide length difference ΔL, for demultiplexing the wavelength division multiplexed optical signal input to the input optical fiber; An optical slab waveguide comprising: an output-side slab waveguide connected to the arrayed waveguide; and a plurality of output-side waveguides connected to the output-side slab waveguide and each outputting a demultiplexed optical signal to an output optical fiber. In the duplexer,
A band adjusting waveguide element is provided between an input optical fiber and an input side slab waveguide.

In addition to the above configuration, the wavelength multiplexer / demultiplexer according to the present invention comprises:
It is preferable that a plurality of additional waveguides are arranged near the band adjusting waveguide element and the output side waveguide, respectively.

In addition to the above configuration, the wavelength multiplexer / demultiplexer of the present invention comprises:
Preferably, each waveguide is a temperature independent waveguide.

According to the present invention, a band adjusting waveguide element is provided between an input optical fiber and an input side slab waveguide, and the position and shape of the band adjusting waveguide element are optimized to provide a wide band. Waveform adjustment such as conversion can be performed. By arranging the additional waveguides in the band adjusting waveguide and the output side waveguide, even if a slight axis shift occurs when these elements are fixed, the center wavelength can be accurately set by the combination of the waveguides. it can.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1A is a plan view showing an embodiment of the optical wavelength multiplexer / demultiplexer according to the present invention, and FIG. 1B is a band diagram of the optical wavelength multiplexer / demultiplexer shown in FIG. FIG. 1C is an enlarged plan view of a region A in FIG. 1A, and FIG.
FIG. 1D is a partially enlarged view of a region B in FIG.
1 is a partially enlarged view of a region C in FIG. 1A, and FIG.
It is DD sectional drawing of (a). Note that the same members as those in the conventional example shown in FIG.

This optical wavelength multiplexer / demultiplexer comprises a substrate (for example, a quartz substrate) 1, an input-side slab waveguide 10 formed on the substrate 1 for inputting a wavelength division multiplexed optical signal from an input optical fiber 2. An array waveguide 4 which is connected to the input side slab waveguide 10 and has a plurality of waveguides 4a having a predetermined waveguide length difference ΔL, and which demultiplexes the wavelength division multiplexed optical signal input to the input optical fiber 2; An output-side slab waveguide 5 connected to the arrayed waveguide 4, a plurality of output-side waveguides 7b connected to the output-side slab waveguide 5, and outputting the demultiplexed optical signals to the output optical fiber 6, respectively; A band-adjusting waveguide element 11 provided between the input optical fiber 2 and the input-side slab waveguide 10, and additional waveguides disposed near the band-adjusting waveguide element 11 and the output-side waveguide 7b, respectively. 7
a and 13a. Each waveguide is a temperature-independent waveguide. 15 is a buffer layer, 16
Is a waveguide core, and 17 is a cladding layer.

The input side slab waveguide 10 has an output end face (right end face in the figure) formed in an arc shape, whereas the input end face (left end face in the figure) has a straight line so as to be the same as the end face of the substrate 1. It is formed in a shape.

The band adjusting waveguide element 11 includes a substrate 12 made of the same material as the substrate 1, an additional waveguide 13 a formed on the substrate 12, and having one end (the left end in the figure) connected to the input optical fiber 2. Input side waveguide 13b and additional waveguide 1
3a and a slab waveguide 14 connected to the other end (right end in the figure) of the input side waveguide 13b. The input end face of the slab waveguide 14 is formed in an arc shape, while the output end face is formed linearly so as to be the same as the end face of the substrate 12. Bandwidth adjusting waveguide element 11
Is formed so that the waveguide core exposed at the output end face of the slab waveguide 14 is optically connected to the waveguide core exposed at the input end face of the input side slab waveguide 10 of the substrate 1.

In this optical wavelength multiplexer / demultiplexer, a band adjusting waveguide element 11 is provided between the input optical fiber 2 and the input side slab waveguide 10, and the position and shape of the band adjusting waveguide element 11 are changed. By optimizing, it is possible to perform waveform adjustment such as widening of the bandwidth. In addition, in order to accurately set the center wavelength, the band adjustment waveguide element 11 and the output side waveguide 7 are used.
The additional waveguides are arranged in the vicinity of b, and even if a slight axis shift occurs when these elements are fixed, the center wavelength can be set accurately by the combination of the waveguides.

[0023]

Next, specific numerical values will be described, but the present invention is not limited to them.

The design parameter of the temperature-independent type optical wavelength multiplexer / demultiplexer is such that the demultiplexing interval is 0.8 nm (100 GHz).
And the number of channels was set to 16. The waveguide pitch ΔX1 at the boundary between the band adjusting waveguide element 11 and the input side slab waveguide 10 is set to 21 μm, and the output side slab waveguide 5
Pitch Δ at the boundary between the waveguide and the output side waveguide 7b
X2 was about 20 μm. According to this design parameter, when connecting the band adjustment waveguide element 11 to the input side slab waveguide 10, if there is a displacement of, for example, 1 μm in the X direction, the demultiplexing at a frequency of about 5 GHz (wavelength 0.04 nm). A wavelength shift occurs.

However, since the waveguide pitch ΔX1 of the input side waveguide 13b is 1.05 times the pitch of the output side waveguide 7b, shifting the input side waveguide 13b by one port allows the output side waveguide 7b to be shifted. The frequency of the split light is about 10
Shift by 5 GHz (wavelength: about 0.84 nm). Therefore, by appropriately combining the plurality of input-side waveguides 13b and the output-side waveguides 7b, fine adjustment of the demultiplexed wavelength of several GHz (several tens of pm in frequency) can be performed.

In this embodiment, the number of the input side waveguides 7b and the number of the additional waveguides 7a is set to 13, and the number of the output side additional waveguides 7a
, Six on each side, for a total of twelve. That is, the additional waveguide 7a and the output waveguide 7b extended to the output side
Are 28.

The band adjusting waveguide element 11 has a Y-branch structure for the purpose of broadening the band. The band adjusting waveguide element 11 is connected to the input side slab waveguide 10 of the temperature independent array waveguide type optical wavelength multiplexer / demultiplexer main body. In order to match the transmission wavelength with the international standard, the connection of the band adjusting waveguide element 11 was adjusted by slightly moving in the X direction.
Between the input optical fiber 2 and the band adjusting waveguide element 11;
The connection end faces between the band adjustment waveguide element 11 and the input side slab waveguide 10 and between the output side waveguide 7b and the output optical fiber 6 are obliquely polished at 8 ° to reduce the return loss. .

The band adjustment waveguide element 11 and the optical wavelength multiplexer / demultiplexer main body use quartz for the substrates 1 and 12,
6, the refractive index of 1.4692, and the refractive index of the cladding layer 17 of 1.4692.
4574. The waveguide core 16 was formed by a photolithography technique and an etching technique, and then a clutch was deposited by a flame deposition technique. When the substrates 1 and 12 are made of quartz, the buffer layer 15 need not be deposited.

FIG. 2 is a diagram showing the demultiplexing wavelength characteristics of the optical wavelength multiplexer / demultiplexer shown in FIGS. 1 (a) to 1 (f). The horizontal axis is the input port number axis, and the vertical axis is the demultiplexing. It is a wavelength axis.

By selecting a combination of input and output ports, the transmission wavelength changes in steps of about 0.04 nm,
Fine adjustment of the center wavelength, which was difficult in the past, has become possible.

FIG. 3 is a diagram showing the wavelength loss characteristics of the optical wavelength multiplexer / demultiplexer shown in FIGS. 1 (a) to 1 (f). The horizontal axis is the wavelength axis, and the vertical axis is the loss axis.

By using the Y-branch structure for the band adjusting waveguide element, a broadband and flattened waveform which cannot be obtained by the conventional method of directly connecting the optical fiber to the end face of the slab waveguide is obtained. The obtained waveform was equivalent to that of a multiplexer / demultiplexer in which a band-adjusting waveguide element and an arrayed waveguide type multiplexer / demultiplexer, which were prototyped by a conventional heater temperature control method, were integrated.

In this embodiment, the demultiplexing interval is 100 G
Although an optical wavelength multiplexer / demultiplexer having 16 Hz and 16 channels has been described, the present invention is not limited to this, and the demultiplexing interval, the number of channels, and the like can be arbitrarily set. In addition to the Y-branch structure as the band adjusting waveguide element, a parabolic horn structure (FIG. 4A) and an MMI structure (FIG.
(B)) and a structure such as a tapered structure (FIG. 4C) may be used.

4 (a) to 4 (c) correspond to FIG. 1 (a).
FIGS. 2A to 2F are modifications of the band adjusting waveguide element shown in FIG.

As described above, according to the present invention, a band adjusting waveguide element is provided between an input optical fiber and an arrayed waveguide type optical wavelength multiplexing / demultiplexing element, and the band adjusting waveguide element has an appropriate structure. By doing so, it is possible to make adjustments such as broadening the band. In addition, in order to accurately set the center wavelength, an additional waveguide is disposed in each of the optical wavelength multiplexer / demultiplexer of the band adjusting waveguide element and the array waveguide, and even if a slight axis shift occurs when these elements are fixed. By combining the waveguide elements, the center wavelength can be accurately set.

[0036]

In summary, according to the present invention, the following excellent effects are exhibited.

Flattening can be achieved in a wide band, the center wavelength can be set with high accuracy, and an optical wavelength multiplexer / demultiplexer with low crosstalk can be provided.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of an optical wavelength multiplexer / demultiplexer according to the present invention, and FIG. 1B is a waveguide element for band adjustment of the optical wavelength multiplexer / demultiplexer shown in FIG. (C) is an enlarged view of the area A in (a), (d) is a partially enlarged view of the area B in (a), (e) is a partially enlarged view of the area C in (a),
(F) is a sectional view taken along line DD of (a).

FIG. 2 is a diagram illustrating demultiplexing wavelength characteristics of the optical wavelength multiplexer / demultiplexer illustrated in FIGS. 1 (a) to 1 (f).

FIG. 3 is a diagram showing wavelength loss characteristics of the optical wavelength multiplexer / demultiplexer shown in FIGS. 1 (a) to (f).

4 (a) to 4 (c) are modifications of the band adjusting waveguide element shown in FIGS. 1 (a) to 1 (f).

FIG. 5 is a plan view showing a conventional example of a wavelength multiplexer / demultiplexer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 4 Array waveguide 5 Output side slab waveguide 7 Output side waveguide 7a, 13a Additional waveguide 10 Input side slab waveguide 13 Input side waveguide 14 Slab waveguide

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Naoto Uezuka 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture F-term in Opto-Systems Research Laboratory, Hitachi Cable, Ltd. 2H047 KA03 KA12 KA15 KB10 LA18 MA05 TA00

Claims (3)

[Claims] 1. A substrate, an input slab waveguide formed on the substrate for inputting a wavelength division multiplexed optical signal from an input optical fiber, and a predetermined waveguide length difference ΔL connected to the input slab waveguide. An arrayed waveguide composed of a plurality of waveguides having the following configuration and splitting the wavelength division multiplexed optical signal input to the input optical fiber; an output side slab waveguide connected to the arrayed waveguide; In an optical wavelength multiplexer / demultiplexer including a plurality of output-side waveguides each connected to a slab waveguide and outputting a demultiplexed optical signal to an output optical fiber, the input optical fiber, the input-side slab waveguide, An optical wavelength multiplexing / demultiplexing device characterized in that a band adjusting waveguide element is provided between them. 2. The wavelength multiplexer / demultiplexer according to claim 1, wherein a plurality of additional waveguides are arranged in the vicinity of the band adjusting waveguide element and the output side waveguide, respectively. 3. The optical wavelength multiplexer / demultiplexer according to claim 1, wherein each of the waveguides is a temperature-independent waveguide.