JP2003114356A - Temperature compensation type optical communication interference device and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized temperature compensation type optical communication interference device in which the temperature dependency of light transmission characteristics is reduced. SOLUTION: A 1st port 121 and a 2nd port 122, a half-mirror 123, and a 1st mirror 124 and a 2nd mirror 125 which constitute an optical system of a Michelson interferometer are fixed at respective positions on a substrate 126, and a 1st member 126a and a 2nd member 126b are combined whose signs of a coefficient of linear expansion are different to each other. The 1st port 121 and 2nd port 122, half-mirror 123, and 1st mirror 124 and 2nd mirror 125 are fixed on the 1st member respectively. The total-reflecting mirror 124b and 2nd mirror 125 are fixed on the 2nd member 126b respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device that splits input light into two and then outputs the light by interfering the two.

[0002]

2. Description of the Related Art Mach-Zehnder interferometer type devices and Michelson interferometer type devices are known as optical devices for dividing input light into two and then interfering the two and outputting them.

The Mach-Zehnder interferometer type optical device is
A first optical coupler (optical branching means) and a second optical coupler (optical coupling means) are provided, and a first optical path and a second optical path are provided between the first optical coupler and the second optical coupler. In this optical device, the light input from the input end is branched into two by a first optical coupler, one branched light is propagated through a first optical path, and the other branched light is propagated through a second optical path, and , The light arriving via each of the first optical path and the second optical path is output to the output end together by the second optical coupler. The transmission characteristic of light from the input end to the output end in this optical device depends on the optical coupling characteristics of the first optical coupler and the second optical coupler, and the difference in optical path length of the first optical path and the second optical path. is doing.

Further, the Michelson interferometer type optical device is provided with a half mirror serving as both an optical branching means and an optical coupling means, a first mirror and a second mirror, and the light output from the half mirror is the first mirror. The first optical path that is reflected by and returns to the half mirror, and the second light that is output from the half mirror is reflected by the second mirror and returns to the half mirror.
It has an optical path. In this optical device, the light inputted from the input end is branched into two by a half mirror, and one of the branched lights is propagated along a first optical path (a round-trip optical path between the half mirror and the first mirror) and is branched. The other light is the second optical path (reciprocal optical path between the half mirror and the second mirror)
And propagated through the first optical path and the second optical path, and output to the output end together by the half mirror. The transmission characteristic of light from the input end to the output end in this optical device depends on the optical branching characteristic of the half mirror and the difference in optical path length between the first optical path and the second optical path.

Such an optical device can be used as an optical filter having a certain loss spectrum in an optical communication system, or can be used as an interleaver that alternately multiplexes and demultiplexes signal lights of multiple wavelengths.

[0006]

As described above, the light transmission characteristic of the Mach-Zehnder interferometer type or Michelson interferometer type optical device depends on the difference in the optical path lengths of the first optical path and the second optical path. There is. Therefore, each optical component forming the optical device is fixed on the substrate so that the optical transmission characteristic of the optical device is maintained constant, and the difference in optical path length between the first optical path and the second optical path is maintained constant. It

However, when each optical component constituting the optical device is fixed on the substrate, the optical path lengths of the first optical path and the second optical path change in accordance with the expansion and contraction of the substrate due to the temperature change. However, the difference in optical path length between the two also changed,
The light transmission characteristics of the optical device change. As described above, the light transmission characteristics of the optical device have temperature dependence.

In order to solve such a problem, it may be possible to keep the temperature of the entire optical device constant. However, in this case, it is necessary to provide temperature adjusting means for maintaining the temperature constant, and it is also necessary to provide means for supplying electric power to the temperature adjusting means. Will be the one.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a small temperature-compensated optical communication interference device in which the temperature dependence of light transmission characteristics is reduced.

[0010]

The temperature-compensated optical communication interference device according to the present invention comprises: (1) Two types of light input from an input end.
Optical branching means for branching and outputting one branched light to the first optical path, and outputting the other branched light to the second optical path, (2)
An optical coupling means for inputting the light arriving via each of the first optical path and the second optical path and outputting the light together to an output end; and (3) an optical component on the optical path of the first optical path and a second optical path. And a substrate for fixing each of the optical components on the optical path, the optical branching means, and the optical coupling means. Further, the substrate has a first member and a second member which have different coefficients of linear expansion.
A member is combined, and based on the difference in the sign of the linear expansion coefficient of each of the first member and the second member,
The temperature dependence of the difference between the optical path lengths of the first optical path and the second optical path is reduced.

According to the present invention, the light inputted from the input end is branched into two by the optical branching means, one of the branched light reaches the optical coupling means through the first optical path, and the other branched light. Reaches the optical coupling means via the second optical path, and both are output to the output end by the optical coupling means. The lights that have passed through the first optical path and the second optical path interfere with each other when both are output to the output end by the optical coupling means. Therefore, the transmission characteristics of the light from the input end to the output end are It depends on the difference in optical path length between the two optical paths. On the other hand, each of the optical component on the optical path of the first optical path, the optical component on the optical path of the second optical path, the optical branching means, and the optical coupling means is a combination of a first member and a second member having different signs of linear expansion coefficients. It is fixed on the substrate. Then, based on the difference in the signs of the linear expansion coefficients of the first member and the second member,
The temperature dependence of the difference between the optical path lengths of the first optical path and the second optical path is reduced. As a result, the temperature dependence of the light transmission characteristics of the temperature-compensated optical communication interference device is reduced without providing temperature adjusting means for maintaining the temperature constant.

The temperature compensation type optical communication interference device according to the present invention may be of a Mach-Zehnder interferometer type or a Michelson interferometer type. The temperature-compensated optical communication interference device can be used as an optical filter having a certain loss spectrum in an optical communication system, or can be used as an interleaver that alternately multiplexes and demultiplexes signal lights of multiple wavelengths.

An optical communication system according to the present invention is characterized in that the above-mentioned temperature-compensated optical communication interference device according to the present invention is provided on a transmission path along which multi-wavelength signal light propagates.
Since this optical communication system includes the temperature compensation type optical communication interference device described above, the temperature dependence of the transmission characteristics of the signal light is reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

An optical filter 120 and an interleaver 100 including the same will be described as an embodiment of a temperature compensation type optical communication interference device according to the present invention. FIG. 1 is a configuration diagram of an interleaver 100 and an optical filter 120 according to this embodiment. This interleaver 100
An optical circulator 110 and an optical filter 120 are provided.

The optical circulator 110 has a first terminal 11
1, having a second terminal 112 and a third terminal 113, outputs the light input to the first terminal 111 via the optical fiber 101 to the optical fiber 102 from the second terminal 112, and outputs the light via the optical fiber 102. The light input to the second terminal 112 is output to the optical fiber 103 from the third terminal 113.

The optical filter 120 includes a first port 121,
Second port 122, half mirror 123, first mirror 1
24, a second mirror 125 and a substrate 126. The first port 121 of the optical filter 120 is connected to the optical fiber 10
It is connected to the second terminal 112 of the optical circulator 110 via 2.

The optical system including the first port 121, the second port 122, the half mirror 123, the first mirror 124, and the second mirror 125 constitutes a Michelson interferometer. That is, the half mirror 123 has the first port 1
The light arriving from 21 is branched into two, and one of them is divided into the first mirror 1
24, and the other is output to the second mirror 125. The half mirror 123 splits the light reflected and arriving by the first mirror 124 into two, and outputs one to the first port 121 and the other to the second port 122. The half mirror 123 splits the light reflected by the second mirror 125 and arriving into two,
One is output to the first port 121 and the other is output to the second port 122.

The first mirror 124 includes a half mirror 124a having a transmittance of several tens% and a total reflection mirror 124b.
It has a res-Tournois resonator configuration. That is, the half mirror 124a and the total reflection mirror 124b are parallel to each other, and the half mirror 124a reflects a part of the light reaching from the half mirror 123 and transmits the rest to the total reflection mirror 124b. The half mirror 124a and the total reflection mirror 124b repeatedly reflect the light transmitted through the half mirror 124a between the two, and partially transmit the light through the half mirror 124a, so that the half mirror 12
Output to 3. As a result, the first mirror 124 is
The reflection characteristic has wavelength dependence, and the reflectance repeatedly changes between 0% and 100% with respect to the wavelength. Further, the cycle (wavelength interval) of the reflectance change is determined by the optical distance between the half mirror 124a and the total reflection mirror 124b.

The substrate 126 fixes the positions of the first port 121, the second port 122, the half mirror 123, the first mirror 124, and the second mirror 125, which form the optical system of the Michelson interferometer. The first member 126a and the second member 126b having different signs of linear expansion coefficients are combined. 1st port 1
21, the second port 122, the half mirror 123, and the half mirror 124a are fixed on the first member 126a. The remaining total reflection mirror 124b and the second mirror 125 are fixed on the second member 126b.

In the following, in the first optical path P ₁ in which one of the two beams branched by the half mirror 123 is reflected by the first mirror 124 and returns to the half mirror 123, the optical path from the half mirror 123 to the half mirror 124a. Let L ₁ be the length. In the second optical path P ₂ where the other light split into two by the half mirror 123 is reflected by the second mirror 125 and returns to the half mirror 123, the optical path length from the half mirror 123 to the second mirror 126 is L.
_Set to ₂ . Then, L ₁ <L ₂ . Also, the first member 1
The coefficient of linear expansion of 26a is β ₁ , the coefficient of linear expansion of the second member 126b is β ₂ , and the coefficient of linear expansion β ₁ and the coefficient of linear expansion β ₂
And the signs are different from each other.

In the first optical path P ₁ , the entire optical path length L ₁ is on the first member 126a. On the other hand, in the second optical path P ₂ , of the optical path length L ₂ , the portion having the optical path length (L ₁ + L ₂₁ ) from the half mirror 123 is on the first member 126a, and the remaining optical path length L ₂₂ is the second portion. It is on the member 126b. However, between these parameters

[Equation 1] The sizes of the first member 126a and the second member 126b are determined so that the following relational expression holds.

At this time, if the temperature changes by ΔT, the optical path length in the first optical path P ₁ is changed from the initial L ₁ to

[Equation 2] Changes to. On the other hand, when the temperature changes by ΔT, the optical path length in the second optical path P ₂ is changed from the initial L ₂ to

[Equation 3] Changes to. Therefore, if the optical path length difference ΔL ′ when the temperature changes by ΔT is considered in the above equation (1),

[Equation 4] And is equal to the optical path length difference before temperature change. That is, based on the difference in the signs of the linear expansion coefficients of the first member 126a and the second member 126b, the first optical path P ₁
The temperature dependence of the difference between the optical path lengths of the second and second optical paths P ₂ is reduced.

In the optical path between the half mirror 124a and the total reflection mirror 124b, the half mirror 124a is included.
The optical path length L ₁₁ on the side is on the first member 126a, and the optical path length L ₁₂ on the side of the remaining total reflection mirror 124b is on the second member 126b.
It is above. However, between these parameters

[Equation 5] The sizes of the first member 126a and the second member 126b are determined so that the following relational expression holds. By doing so, the temperature dependence of the optical path length between the half mirror 124a and the total reflection mirror 124b is reduced based on the difference in the signs of the linear expansion coefficients of the first member 126a and the second member 126b. It

The interleaver 100 operates as follows. The light propagating through the optical fiber 101 is input to the first terminal 111 of the optical circulator 110, is output from the second terminal 112, and is transmitted through the optical fiber 102 to the first terminal 111.
Input to the optical filter 120 from the port 121. The light input from the first port 121 of the optical filter 120 is branched into two by the half mirror 123, one of the two branched lights is output to the first optical path P ₁ , and the other of the two branched lights is the second light. It is output to the optical path P ₂ .

The light output from the half mirror 123 to the first optical path P ₁ reciprocates to and from the first mirror 124, returns to the half mirror 123, is branched into two by the half mirror 123, and is branched into two. Light is output to the optical fiber 102 from the first port 121, and the other light branched into two is output to the optical fiber 104 from the second port 122. Further, the light output from the half mirror 123 to the second optical path P ₂ reciprocates between the second mirror 125 and the half mirror 123, returns to the half mirror 123, and is branched into two by the half mirror 123. The light is output from the first port 121 to the optical fiber 102, and the other light split into two is output to the optical fiber 104 from the second port 122.

From the half mirror 123 to the optical fiber 102
The light output to is the light that reaches the half mirror 123 from each of the first optical path P ₁ and the second optical path P _{2 and} is partly superimposed and interferes with each other. This optical fiber 102
The light output to the optical circulator 110 is input to the second terminal 112 of the optical circulator 110 and is output from the third terminal 113 to the optical fiber 103.
Is output to. On the other hand, the light output from the half mirror 123 to the optical fiber 104 is a part of the light reaching the half mirror 123 from each of the first optical path P ₁ and the second optical path P _{2 and} is superimposed and interferes with each other.

In this interleaver 100, the first mirror 124 in the optical filter 120 is a Gires-Tournois.
It has a structure of a resonator, and its reflection characteristic has wavelength dependence. From this, the interleaver 100 has more wavelengths (λ ₁ ,
_{λ 2, ..., λ 2n-} 1, λ 2n, ...) demultiplexed by inputting signal light, the first wavelength band _{Λ 1 (λ 1, λ 3} , ..., λ 2n-1, ...) signal The light is output to the optical fiber 104, and the second wavelength band Λ
₂ (λ ₂ , λ ₄ , ..., λ _2n , ...) Signal light
Can be output to 03. Where λ ₁ <λ ₂ <... <
λ _2n-1 <λ _2n <..., and the wavelength intervals of these multi-wavelength signal lights are the half mirror 124 a and the total reflection mirror 12.
It is determined by the optical distance from 4b.

Further, in the interleaver 100, as described above, the temperature dependence of the difference (L ₂₁ + L ₂₂ ) in the optical path lengths of the first optical path P ₁ and the second optical path P ₂ is reduced, Half mirror 124a in the first mirror 124
Optical path length (L ₁₁ + L ₁₂ ) between the mirror and the total reflection mirror 124b
Also has reduced temperature dependence. Therefore, the transmission characteristics of light in the first wavelength range Λ ₁ from the optical fiber 101 to the optical fiber 104 and the transmission characteristics of light in the second wavelength range Λ ₂ from the optical fiber 101 to the optical fiber 103 are
The temperature dependence is reduced.

Next, the interleaver 1 according to the present embodiment.
A specific example of No. 00 will be described. Assuming that an interleaver 100 that demultiplexes multi-wavelength signal light with a frequency interval of 100 GHz is assumed, the interference frequency period (FSR: Free Spectral Range) is 100 G.
Since it is Hz, the difference (L ₂₁ + L ₂₂ ) between the optical paths of the first optical path P ₁ and the second optical path P ₂ is 1.498570 mm. The first member 126a is made of stainless steel SUS304 and has a linear expansion coefficient β ₁ of 1.73 × 10 ⁻⁵ . On the other hand, the second member 126b is made of ceramic (CERSAT (trade name) manufactured by Nippon Electric Glass Co., Ltd.) and has a linear expansion coefficient β ₂ of −8.2 × 10 ⁻⁶ . From this, considering the above equation (1), the optical path length L ₂₁ is 0.481.
9 mm, and the optical path length L ₂₂ is 1.01667 mm.

Next, the optical communication system 1 according to the present embodiment
Will be described. FIG. 2 is a configuration diagram of the optical communication system 1 according to the present embodiment. This optical communication system 1 includes optical transmitters 11 and 12, a multiplexing interleaver 20, an optical fiber transmission line 30, a demultiplexing interleaver 40, and
The optical receivers 51 and 52 are provided. Each of the multiplexing interleaver 20 and the demultiplexing interleaver 40 has the same configuration as the interleaver 100 according to the present embodiment described above, and the temperature dependence of the light transmission characteristics is reduced. . Further, since it is not necessary to provide a temperature adjusting means for keeping the temperature constant, the interleaver 1
00 is small.

On the other hand, the optical transmitter 11 has a first wavelength band Λ.
The signal light of ₁ (λ ₁ , λ ₃ , ..., λ _2n-1 , ...) _Is multiplexed and output. The other optical transmitter 12 uses the second wavelength band Λ.
₂ (λ ₂ , λ ₄ , ..., λ _2n , ...) Signal lights are multiplexed and output. Then, the multiplexing interleaver 20 receives the multi-wavelength signal light of the first wavelength band Λ ₁ output from the optical transmitter 11 and the multi-wavelength of the second wavelength band Λ ₂ output from the optical transmitter 12. The signal light is input, and these are multiplexed and sent out to the optical fiber transmission line 30. The demultiplexing interleaver 40 demultiplexes the multi-wavelength signal lights of the first wavelength band Λ ₁ and the second wavelength band Λ ₂ that have propagated through the optical fiber transmission line 30 and arrive at the first wavelength band Λ 2. Optical receiver 5 for signal light with multiple wavelengths of ₁
1 and outputs the multi-wavelength signal light in the second wavelength band Λ ₂ to the optical receiver 52. One optical receiver 51 receives the signal lights of multiple wavelengths in the first wavelength band Λ ₁ , demultiplexes them, and receives the signal lights of each wavelength. The other optical receiver 52 uses the second wavelength band Λ ₂
The multi-wavelength signal light is input, demultiplexed, and the signal light of each wavelength is received.

In this optical communication system 1, each of the multiplexing interleaver 20 and the demultiplexing interleaver 40 has the same configuration as that of the interleaver 100 described above, and the temperature dependence of the light transmission characteristics is reduced. It was done. Therefore, the transmission quality of the signal light in this optical communication system 1 also has reduced temperature dependence.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, the temperature-compensated optical communication interference device according to the present invention is not limited to the Michelson interferometer type interleaver or optical filter described above, but may be a Mach-Zehnder interferometer.

[0035]

As described above in detail, according to the present invention, the optical components constituting the optical system of the temperature compensation type optical communication interference device have the first and second different coefficients of linear expansion.
It is fixed on a substrate formed by combining the member and the second member. Then, the temperature dependence of the difference between the optical path lengths of the first optical path and the second optical path is reduced based on the difference in the signs of the linear expansion coefficients of the first member and the second member. This reduces the temperature dependence of the light transmission characteristics of the temperature-compensated optical communication interference device. Further, since it is not necessary to provide a temperature adjusting means for keeping the temperature constant,
This temperature-compensated optical communication interference device becomes compact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an interleaver 100 and an optical filter 120 according to the present embodiment.

FIG. 2 is a configuration diagram of an optical communication system 1 according to the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical communication system, 11, 12 ... Optical transmitter, 20 ... Combining interleaver, 30 ... Optical fiber transmission line, 40 ...
Demultiplexing interleaver, 51, 52 ... Optical receiver, 100
… Interleaver, 110… Optical circulator, 120
... Optical filter, 121 ... First port, 122 ... Second port, 123 ... Half mirror, 124 ... First mirror, 12
5 ... 2nd mirror, 126 ... Substrate.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomomi Sano             Sumitomoden 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa             Ki Industry Co., Ltd. Yokohama Works

Claims (2)

[Claims] 1. Light splitting means for splitting light input from an input end into two, outputting one split light to a first optical path, and outputting the other split light to a second optical path; Optical coupling means for inputting the light arriving via each of the optical path and the second optical path and outputting the light together to an output end, an optical component on the optical path of the first optical path, and an optical path of the second optical path. Optical component, a substrate for fixing each of the optical branching unit and the optical coupling unit, and the substrate is a combination of a first member and a second member having different signs of linear expansion coefficients. Reducing the temperature dependence of the difference between the optical path lengths of the first optical path and the second optical path based on the difference in the signs of the linear expansion coefficients of the first member and the second member. Temperature compensated optical communication interference device. 2. An optical communication system comprising the temperature-compensated optical communication interference device according to claim 1 on a transmission path along which multi-wavelength signal light propagates.