JP2000241838A - Digital thermo-optic optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital thermooptic optical switch which permits to obtain the performance equivalent to standard with small operation power and is also reduced in power consumption of an optical cross-connect system and an optical add-drop multiplexer. SOLUTION: This is a digital thermooptic optical switch formed of a Y- branching optical waveguide consisting of a linear optical waveguide 11, a tapered optical waveguide 12, and a branching optical waveguide 13, and a thin film heater 15 along the Y-branching optical waveguide. In this case, the thin film heater 15 part in an area B along the tapered optical waveguide 12 is formed to be gradually tapered in width (maximum width W1 → minimum width W0) from the linear optical wveguide 11 side toward the branching optical waveguide 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wavelength division multiplexing (WD)
M) An optical waveguide type optical switch used for optical path switching in optical communication such as optical communication and optical signal processing, and particularly to a digital thermo-optical switch.

[0002]

2. Description of the Related Art An optical waveguide type thermo-optical switch has no moving parts, has a low insertion loss, is small in size, and can be easily integrated. Promising for use. Among these optical waveguide type thermo-optical switches, digital thermo-optical switches are noted for their advantage that their switch characteristics are basically low dependent on wavelength, polarization and operating power. (Reference 1: N. Ooba et al., “Low Loss 1 × 8 digital optica
l switch and tunable arrayed-waveguide grating mul
tiplexer using a silicone resin waveguide ”, Proc.
7th Int Plastic Opt.Fibres Conf., Berlin, P.303,199
8).

Since the operation of the digital thermo-optical switch requires a large change in the thermo-optical refractive index, a polymer optical waveguide material having a large thermo-optical constant is mainly used for both the core and the clad.

FIG. 4 is a plan view showing the structure of a conventional general digital thermo-optical switch. Along the Y-branch optical waveguide composed of the linear optical waveguide 11, the taper optical waveguide 12, the branch optical waveguide 13, and the output optical waveguide 14 as the input optical waveguide, the thin film heaters 15 are arranged at substantially constant intervals in the vertical direction. ing. 4, the thin film heater 15
The lead for supplying current to the power supply is omitted. The two branch optical waveguides 13 form a tapered velocity coupler that gradually separates while being mode-coupled to each other.

If one of the pair of thin film heaters 15 is heated to make the refractive index of the two branch optical waveguides 13 asymmetric by the thermo-optic effect, the fundamental mode light in the tapered velocity coupler is output from the output optical waveguide 14. The side concentrates on the high refractive index side. Therefore, if the fundamental mode light incident on the linear optical waveguide 11 is not coupled to a higher-order mode, it is guided to the output optical waveguide 14 on the high refractive index side, and this device operates as a branch switch (Ref. 2: WKBurns). , et al., “Mode conversion in planar-
dielectric separating waveguides ”, IEEE j.Quantum
Electron., Vol. QE-11, p. 32, 1975).

In order to obtain a higher branching ratio in the digital thermo-optical switch, it is necessary to reduce the branching angle or to provide a large difference in refractive index to the branching optical waveguide 13. When the branch angle is reduced, the length of the branch optical waveguide 13 that is the heating region becomes longer. In order to obtain an extinction ratio exceeding 20 dB, the branch angle is generally about 0.1 degree, and 10 mm
A small amount of the branch optical waveguide 13 and the thin film heater 15 are required (Reference 3: W. Horsthuis et al., "PACKAGED POLYM"
ERIC 1 × 8 DIGITAL OPTICAL SWITCHES ", Proc. 21st Eu
r.Conf.Opt.Comm., Brussels, Th.L.3,4, p.1059,199
Five).

However, in the case of the polymer optical waveguide, the waveguide loss of the waveguide itself is expected to be about 0.5 dB at 10 mm, so that there is a problem that the loss increases when the switch is long.

Further, a large difference in the refractive index is caused by the branch optical waveguide 13.
, Excessive loss due to mode conversion occurs at the end point of the thin-film heater 15 on the side of the linear optical waveguide 11.
In order to prevent this, a region where the thin film heater 15 is gradually approached to the core (optical waveguide) 12 is required as shown by A in FIG.

[0009]

As described above, in the conventional digital thermo-optical switch, the heating amount of the core portion is controlled by changing the distance between the core and the thin film heater. But,
In this conventional method, in a portion where the amount of heating is desired to be reduced, a region which is not involved in the switching operation and is away from the core is heated, and the heating power efficiency is reduced. Therefore,
In such a digital thermo-optical switch, it has been a problem to increase the heating efficiency and further reduce the power consumption.

An object of the present invention is to solve the above-mentioned problems of the prior art, achieve the same performance with a small operating power, and reduce the power of an optical cross-connect system and an optical add / drop multiplexer. A digital thermo-optical switch is provided.

[0011]

In order to achieve the above object, the present invention is directed to a Y-branch optical waveguide comprising a linear optical waveguide, a tapered optical waveguide, and a branch optical waveguide;
In a digital thermo-optical switch configured by a thin film heater along a branch optical waveguide, a shape in which a part of the thin film heater gradually narrows in width from the straight optical waveguide side toward the branch optical waveguide side, and It is characterized in that it has at least one of the shapes whose thickness is reduced.

Here, preferably, the part of the thin film heater is a part along the tapered optical waveguide.

Preferably, the Y-branch optical waveguide is made of an acrylic polymer, an ultraviolet curable epoxy resin, a silicone resin, or a polyimide, or a combination thereof.

[0014]

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

First, the principle of the present invention will be described. Resistivity ρ
When a current i is passed through a strip-shaped thin-film electric heater having a thickness T and a width W made of a metal thin film of

[0016]

(Equation 1)

## EQU1 ## When the width of the heater is equal to or greater than the thickness of the optical waveguide, the temperature rise of the heater can be approximated as being proportional to the amount of heat generated per unit area. From this, it can be seen that by changing the width or thickness of the thin film heater, the temperature at which the heater rises can be changed depending on the location.

(First Embodiment) FIG. 1 is a plan view showing a configuration of a digital thermo-optical switch according to an embodiment of the present invention. 1, the same components as those of the conventional example of FIG. 4 are denoted by the same reference numerals. That is, along the Y-branch optical waveguide composed of the linear optical waveguide 11 as an input optical waveguide, the tapered optical waveguide 12, the branch optical waveguide 13, and the output optical waveguide 14, the thin film heaters 15 are arranged at substantially constant intervals in the vertical direction. Are located. The two branch optical waveguides 13 form a tapered velocity coupler that gradually separates while being mode-coupled to each other.

In the region of FIG. 1B where the tapered optical waveguide 12 is formed, the width W of the thin-film heater 15 is gradually increased toward the linear optical waveguide 11 (minimum width W _0).
→ The maximum width W ₁ ), the amount of heat generation is reduced, and the same effect as that obtained by keeping the heater away from the conventional one is obtained. For example, heater 1
To make the calorific value of 1/10 at the left end of 5,

[0020]

(Equation 2)

[0021] At this time, the entire heat generation amount or heating power P ₁ of the heater 15 in the region B is determined by the width of the heater 15.

[0022]

(Equation 3)

Assuming that the length of the heater 15 in the region B is L,

[0024]

(Equation 4)

## EQU1 ## Here, P ₀ is the calorific value or heating power of the conventional heater of width W ₀ ,

[0026]

(Equation 5)

## EQU1 ##

From the above equation (4), it can be seen that the heating value or heating power P ₁ in the B region of this embodiment is about half of the heating value or heating power P ₀ of the conventional type.
A reduction in heating power of more than 20% is expected for the entire heater 15 including the portion C in FIG. 1 where the branch optical waveguide 13 is formed.

The Y-branch optical waveguide to which the present invention is applied is preferably made of, for example, an acrylic polymer, an ultraviolet-curable epoxy resin, a silicone resin, or a polyimide, or a combination thereof.

(Second Embodiment) FIG. 2 shows a configuration of a digital thermo-optical switch according to another embodiment of the present invention, in which a thickness of a thin film heater is controlled to change an amount of generated heat. It is a figure and a side view. FIG. 2A is a plan view of FIG.
(B), as shown in the side view of FIG.
In the region B where is formed, the thickness T of the heater 15 is gradually increased toward the straight optical waveguide 11 side (minimum thickness T ₀ → maximum thickness T ₁ ) to reduce the calorific value P _1. Has the same effect as moving the heater away from the optical waveguide. For example, 1/10 at the left end of the heater
The calorific value of

[0031]

T ₁ = 10T ₀ (6) At this time, the calorific value or heating power P ₁ of the entire heater in the region B is about ４ of that of the conventional heater having the thickness T ₀ . A reduction in heating power of 30% or more is expected for the entire heater including the region C.

[0032]

Next, embodiments of the present invention will be described specifically.

First Embodiment A Y-branch optical waveguide is formed on a silicon substrate by using a deuterated silicone resin having a refractive index of 1.489 as a core and a deuterated silicone resin having a refractive index of 1.485 as a clad. Produced. The method for producing the silicone resin optical waveguide was in accordance with the method for producing a "thermo-optical device" (JP-A-10-319445) proposed by the present inventors.

The cross-sectional size of the core is 8 μm × 8 μm, the thickness of the lower cladding, and the thickness of the upper cladding on the core are each 14 μm.
m and 12 μm. A gold thin film was formed on the waveguide by a sputtering method, and a strip-shaped thin film resistance heater having the shape shown in FIG. 1 was manufactured by using photolithography and dry etching. Here, W ₀ = 20 μm and W ₁ = 60
μm.

For comparison, a conventional optical switch having a heater having a constant width of 20 μm as shown in FIG. 4 was similarly manufactured.

An LD light source (not shown) having a wavelength of 1.55 μm and two optical power meters (not shown) were connected to the trunk core 11 and the branch core 14, respectively, and the switch characteristics were measured. The ratio of the two branch outputs, ie the extinction ratio is 30
Heater heating power required to exceed dB is 1
The optical switch of the present invention was 120 mW compared to 60 mW. Thereby, it was confirmed that the heating efficiency can be increased and the power consumption can be reduced by applying the present invention.

(Second Embodiment) A Y-branch optical waveguide having the same structure as that of the first embodiment of the present invention is manufactured, and a metal mask 18 is formed on the Y-branch optical waveguide 16 as shown in FIG. A metal thin film 17 having a change in film thickness was deposited by using a sputtering apparatus which was separately installed. Here, 19 is a sputter target of the sputter device. Further, a strip-shaped thin-film resistance heater having the shape shown in FIG. 2 was manufactured by using photolithography and dry etching. Here, T ₀ = 0.05 μm and T ₁ = 0.6 μm.

The extinction ratio was measured in the same manner as in the first embodiment. The heater heating power at which the extinction ratio became 30 dB or more was 100 mW. Thereby, it was confirmed that the heating efficiency can be increased and the power consumption can be reduced by applying the present invention.

[0039]

As described above, according to the present invention,
The same performance can be obtained with an operating power smaller than that of the conventional one, and the effect of reducing the power of the optical cross-connect system and the optical add / drop multiplexer can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a Y-branch digital thermo-optical switch in which a heater width is changed according to a first embodiment of the present invention.

FIG. 2 is a plan view (a) and a side view (b) showing a configuration of a Y-branch digital thermo-optical switch in which a heater thickness is changed according to a second embodiment of the present invention.

FIG. 3 is a schematic view of a sputter thin film deposition apparatus used in an embodiment of the present invention.

FIG. 4 is a plan view showing a configuration of a conventional Y-branch digital thermo-optical switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Straight optical waveguide 12 Taper optical waveguide 13 Branch optical waveguide 14 Output optical waveguide 15 Thin film heater 16 Optical waveguide 17 Metal thin film deposited 18 Mask 19 Sputter target

Claims (3)

[Claims] 1. A digital thermo-optical switch comprising: a Y-branch optical waveguide including a linear optical waveguide, a taper optical waveguide, and a branch optical waveguide; and a thin-film heater along the Y-branch optical waveguide. A portion whose width gradually narrows from the straight optical waveguide side toward the branch optical waveguide side,
And a digital thermo-optical switch having at least one of a shape whose thickness is reduced. 2. The digital thermo-optical switch according to claim 1, wherein the part of the thin film heater is a part along the tapered optical waveguide. 3. The Y-branch optical waveguide is made of an acrylic polymer, an ultraviolet curable epoxy resin, a silicone resin, or a polyimide, or a combination thereof. Or the digital thermo-optical switch according to 2.