KR100609414B1 - Temperature stabilization of all-optical fiber interleaver device and its manufacturing method - Google Patents

Abstract

The present invention relates to an interleaver, a passive optical component device that is applied to transmit information in a bi-directional direction in an optical transmission system, and stabilizes the temperature of an all fiber type interleaver. It relates to a method and a manufacturing method thereof.

To this end, the present invention manufactures 1X2 and 2X2 optical fiber couplers in which two single-mode optical fibers are fused and combines the first and second connection optical fibers to form a structure of an interferometer by giving a predetermined length difference. An all-fiber type interleaver is fabricated, comprising a Mach-Zehnder Interferometer (MZI).

Conventional all-optical interleaver is sensitive to temperature due to the stress applied to the optical fiber in the thermo-optic coefficient of the optical fiber and the structure of the interferometer, but the present design minimizes the stress applied to the connecting optical fiber of the Mach-Zehnder interferometer and Complementary thermal expansion by complementary thermal expansion coefficient to produce an all-fiber-type interleaver that minimizes the wavelength-shift of the light output spectrum with respect to temperature changes.

FBT, MZI, DWDM, optical fiber coupler, optical path difference, bidirectional transmission system, stress, stress, thermo-optic coefficient

Description

Temperature stabilization and manufacturing method of all-optical interleaver device {Thermal Stability and Manufacture of All Fiber Type Interleaver}

1 is a structure diagram of a conventional optical fiber coupler.

Figure 2 is a structure diagram of an optical fiber coupler to be used in the present invention.

3 is a block diagram of a conventional optical interleaver.

4 is a block diagram of a Mahzander interferometer used in the present invention.

5 is a block diagram of an optical interleaver according to the present invention

<Description of the symbols for the main parts of the drawings>

11,12: conventional first and second optical fiber coupler 13,14: first and second optical fiber coupler of the present invention

21,22: first and second input optical fiber 23,24: first and second output optical fiber

25, 26: 1st, 2nd connection optical fiber 31, 32, 33, 34, 35: epoxy

41: inner package of the optical fiber coupler 51: angle between the first and second connection optical fiber

61, 62: stress 71: fixed substrate

81: stress

The optical interleaver is a type of wavelength division multiplexing (WDM) technology and is a technology for transmitting more information in the field of optical communication transmission technology. At this time, the transmission capacity is influenced by the channel spacing of the optical wavelength. For example, DWDM devices having a compact channel spacing of several nm or less (100 μs: 0.8 nm, 50 μs: 0.4 nm) have a channel spacing of several tens of nm ( The transmission capacity can be increased by providing a larger number of channels than a low density wavelength multiplexing / demultiplexer (CWDM) device having 20 nm and 40 nm).

The optical interleaver has to change the wavelength of the optical signal traveling in both directions to reduce the deterioration of the signal due to the light reflection in the two-way optical transmission system. The optical interleaver has a wavelength-interleaved method in which wavelengths are arranged in both directions. The wavelengths of adjacent optical signals to be proceeded alternately are arranged.

By using the optical interleaver, the wavelength shift bidirectional optical transmission system has the following advantages over the conventional unidirectional optical transmission system.

First, since a single optical fiber enables communication between two nodes, the number of optical fibers required for communication between nodes can be reduced by half. Even if the redundant fiber used in the event of a failure is considered, at least two fibers are required in the bidirectional optical transmission device, while at least four fibers are required in the unidirectional optical transmission system.

Second, the optical nonlinearity can be reduced compared to a unidirectional optical transmission system that provides the same transmission capacity per optical fiber. That is, in the bidirectional optical transmission system using the wavelength shift method, the number of channels traveling in the same direction is reduced by half, and the distance between the channels is doubled, thereby reducing the optical nonlinear phenomenon. In particular, among the nonlinear phenomena of the optical fiber, multi-channel nonlinear phenomena such as cross-phase modulation and four-wave mixing may be reduced.

Third, in the bidirectional optical transmission system of the wavelength alternating method, the distance between the channels is doubled, so it is easy to design and manufacture multiplexer / demultiplexer and various optical filters.

fourth. Adopting bidirectional optical transmission technology can increase the spectral efficiency. As mentioned earlier, the nonlinearity of the fiber can be reduced, the bandwidth of the filter for channel selection can be increased, and the spacing between the channels can be reduced, allowing more channels to be accommodated in the limited wavelength band, resulting in transmission per fiber. Dose can be increased.

The manufacturing method of the optical interleaver is manufactured to have the structure of the Mach-Zehnder interferometer, and the classification of the optical interleaver is largely classified by using a Fused Biconical Taper (FBT) coupler and a planer lightwave circuit (PLC). Technology, a technique using a multilayer interference thin film filter. However, the planar waveguide technology requires a separate temperature controller because the manufacturing process is difficult to control the refractive index of the silicon wafer and the temperature characteristics of the external temperature environment are poor. In addition, the multilayer interference thin film filter type is manufactured by coating a multilayer thin film using a dielectric on a substrate, and the insertion loss (insertion loss) characteristics are excellent, but it is very difficult to manufacture with a channel interval of less than 50Ghz. In addition, the above two manufacturing methods require a high initial investment. However, unlike the above two technologies, the fusion fiber coupler can be manufactured with very narrow channel intervals, and because only the optical fiber is used, the insertion loss is very low and the polarization dependency property is excellent. In addition, the initial investment is low and easy to connect with other optical communication passive components.

The first and second optical fiber couplers 11 and 12 for constructing the Mach-Zehnder interferometer of the optical interleaver apply heat to a part of the first and second optical fibers 21, 22, 23, and 24 as shown in FIG. It is manufactured by using fused fiber optic technology (FBT), which is tensioned to produce a change in core diameter and to a symmetrical tapered structure on both sides, and light coupling occurs in this region. The optical fiber couplers 11 and 12 of FIG. 1 manufactured as described above are fixed and packaged to the internal package structure 41 of quartz material using epoxy 31 and 32.

)이 변화하게 된다. 위상차는 식1과 같이 전파상수(k)와 유효경로차(

)에 의해서 표현할 수 있다.The Mahzander interferometer structure has a phase difference ( By the spectral spacing of the output wavelength

) Will change. The phase difference is the difference between the propagation constant (k) and the effective path (

Can be expressed by

)는 전파상수의 차와 유효경로차를 이용하여 식2에 의해서 구할 수 있다. Therefore, the phase difference can be changed by varying the length of the two optical fibers or different propagation constants in the interferometer structure. The optical path difference for obtaining the desired spectral spacing in the change of the phase difference

) Can be obtained from Equation 2 using the difference between the propagation constant and the effective path difference.

)는 식3과 같다. At this time, the channel interval (

) Is the same as Equation 3.

Existing techniques use the above equation 2 as shown in FIG. 3, so that the first and second output optical fibers 23 and 24 and the second and second output optical fibers of the first optical fiber coupler 11 have an optical path difference to obtain a desired channel spacing. After the first and second output optical fibers 23 and 24 of the optical fiber coupler 12 are cut and connected differently, the length of the first and second connection optical fibers 25 and 26 connected by the interferometer is finely adjusted to desired channel spacing. It was adjusted to be.

만큼 변화되어 약0.0085㎚/℃의 파장천이가 생기게 된다. 인터리버 소자의 동작온도범위가 70℃라면 파장천이는 0.595㎚가 된다. 50㎓ 인터리버소자의 채널간격이 0.4㎚이므로 이런 파장천이는 전송시스템에서 심각한 문제를 발생하게 된다.However, the all-fiber interleaver manufactured in this way has a refractive index of optical fiber with temperature.

By a wavelength shift of about 0.0085 nm / ° C. If the operating temperature range of the interleaver element is 70 ° C, the wavelength transition is 0.595 nm. Since the channel spacing of the 50 kHz interleaver is 0.4 nm, this wavelength transition causes serious problems in the transmission system.

In addition, the difference in thermal expansion coefficients of the first and second connection optical fibers 25 and 26 according to the temperature due to the difference in stress 81 applied to the first and second connection optical fibers 25 and 26 having different lengths of the Mahzander interferometer. Due to this, a change in the optical path difference occurs, thereby causing a problem of change in output spectral characteristics and wavelength shift of the interleaver.

In order to solve this problem, the temperature-sensitive problem is solved by maintaining a constant temperature inside the interleaver by using a temperature controller from the outside, but the problem that power is applied and the final package are increased. It has a disadvantage.

)으로 표현할 수 있고 식4와 같다.The first and second connection optical fibers 25 and 26 of the Mahzander interferometer are affected by the temperature change, and the product of the difference between the refractive index and the length difference of the first and second connection optical fibers 25 and 26 (

) Can be expressed as Equation 4.

는 열광학계수, C는 열팽창계수,l₁,l₂은 제1,2 접속 광섬유(25,26)의 길이이다.here,

Is the thermo-optic coefficient, C is the thermal expansion coefficient, and l ₁ and l ₂ are the lengths of the _first and second connection optical fibers 25 and 26.

The present invention changed the structure of the conventional optical fiber coupler to solve the above problems.

In the existing Mahzander interferometer, the first connection optical fiber 25 is more stressed than the second connection optical fiber 26 and the thermo-optic coefficient is large. Since the stress 81 of the optical fiber causes a change in the refractive index according to the temperature change, the present invention minimizes the stress of the first connection optical fiber 25 and reduces the change in the refractive index to reduce the change in the refractive index. The aim is to minimize the change in wavelength and transition.                         

In order to achieve the above object, when the optical fiber couplers 13 and 14 are manufactured as shown in FIG. 2, the first and second connection optical fibers 25 and 26 of the Mahzender interferometer are manufactured as shown in FIG. 4.

In addition, if the temperature characteristic of the optical interleaver is checked, the wavelength shifts toward the longer wavelength when the temperature increases, and when the distance between the two couplers is narrowed, the first and second connection optical fibers 25 and 26 become stress (61, 62), the wavelength shifts toward the longer wavelength. Accordingly, as shown in FIG. 4, an epoxy such as an optical fiber is coated such that the optical fiber contacts the outer portion of the epoxy so that the thermal expansion coefficient has a stress 61 and 62 in a direction opposite to the direction in which the optical fiber moves to the epoxy 34 and 35. Temperature compensation.

Hereinafter, described in detail by the accompanying drawings as follows.

The optical fiber coupler used in the present invention is manufactured using the fusing tension (FBT) technology of the optical fiber as shown in FIG.

The optical fiber couplers 13 and 14 are manufactured by using the heat source for the two optical fibers to melt and stretch the bonding rate by the change of the coupling coefficient in the tapered region according to the tensile length. At this time, since the optical interleaver device has to have uniform output characteristics between adjacent channels in a wide wavelength band, a wideband coupler (WFC: Wavelength Flattened Coupler) having a uniform insertion loss characteristic according to the wavelength is used in the optical fiber coupler.

Existing fusion fiber type coupler is melted and stretched in parallel to each other the first optical fibers (21, 23) and the second optical fibers (22, 24) as shown in Figure 1 epoxy (31, 32) on the inner package structure 41 of the quartz material ).

(51)로 벌어지도록 내부 패키지 구조물(41)에 에폭시(31,32)로 융착부 고정부위가 광섬유 혹은 광섬유 클래드의 지름의 2배보다 크도록 고정하여 패키지 하였다. 각도

(51)는 인터리버의 채널간격에 따라 조정한다.However, in the present invention, as shown in Fig. 2, the first and second optical fibers 21 and 22 of the optical fiber coupler have a constant angle.

The package was fixed to the inner package structure 41 so that the fusion part fixing portion was larger than twice the diameter of the optical fiber or the optical fiber cladding with epoxy (31, 32) so as to open to (51). Angle

Reference numeral 51 adjusts according to the channel interval of the interleaver.

Optical fiber with a micrometer so that the first and second output optical fibers 23 and 24 of the first optical fiber coupler 13 and the first and second output optical fibers 23 and 24 of the second optical fiber coupler 14 have a desired length difference. After cutting the lengths of the first output optical fiber 23 and the second output optical fiber 24 differently using an optical fiber cleaver, the cut optical fibers were connected by using a splicer. Subsequently, the optical path difference was finely tuned by checking the channel spacing with an optical spectrum analyzer (OSA) while melting and stretching the first and second connection optical fibers 25 and 26 in the interferometer.

For example, since the 50 GHz interleaver has a length difference of about 2 mm between the first and second connection optical fibers 25 and 26, the 50 GHz interleaver is formed in the first connection optical fiber 25 of FIG. 3 when it is manufactured with the couplers 11 and 12 as shown in FIG. 1. Since the stress 81 is applied to the package, as shown in FIG. 5, the stress 81 of the first optical fiber 21 is minimized by a coupler as shown in FIG. 2.

In addition, when the temperature increases, the wavelength shifts toward the longer wavelength, and when the distance between the two couplers is narrowed, the first and second connection optical fibers 25 and 26 move in the opposite directions of the stresses 61 and 62 of FIG. At this time, the wavelength shifts toward the longer wavelength. Therefore, as shown in FIG. 4, the optical fiber is positioned at the center of the epoxy so as to have the stresses 61 and 62 in the direction opposite to the direction in which the optical fiber moves to the epoxy 34 and 35 so that the optical fiber contacts the outer portion of the epoxy without being directly fixed. Apply temperature to reverse.

When fixing the optical interleaver manufactured on the fixed substrate 71, the first and second optical fiber couplers 13 and 14 and the first and second connection optical fibers are completely fixed by epoxy 33 so as to be in close contact with each other. In this case, the distance between the first and second optical fiber couplers 13 and 14 may be increased to maintain and fix the intervals to which the tensile force is not applied to the first and second connection optical fibers 25 and 26, thereby producing a stable optical interleaver.

According to the present invention, the optical interleaver increases the transmission capacity by using a wavelength-interleaved method in both directions in a bidirectional transmission system. The temperature compensation is minimized so that the wavelength shift can be applied to the transmission system stably.

In addition, a Dense Wavelength Division Multiplexing (DWDM) device may be manufactured by cascading individual optical interleavers.

At this time, when the temperature characteristics of the individual optical interleaver is different and the wavelength transition according to the temperature becomes large, it becomes difficult to manufacture the DWDM device. When the optical interleaver is manufactured, the DWDM device can be easily manufactured.

Claims (7)

In the first 1X2 or 2X2 optical coupler and the second 2X2 optical coupler, the first optical coupler output terminals and the input terminals of the second optical coupler are optically 1: 1 connected and each optical interference length In the all-optical Mach-Zehnder interferometer having a different structure, at least one interferometer of the two interferometer structures of the output end of the first optical coupler and the input end of the second optical fiber coupler is stressed by having a constant angle, not horizontal. Minimized all-optical Mach-Zehnder interferometer In order to stress or reduce stress in the all-optical Mach-Zenfer interferometer of claim 1, the first optical fiber coupler and the second optical fiber coupler input end are stressed by epoxy on the upper part or the lower part of the two interferometer parts optically connected. One all-optical Mahzander interferometer delete Fusion part fixing part of the first optical fiber coupler and the second optical fiber coupler such that the output terminals of the first optical fiber coupler and the second optical fiber coupler input terminals have a predetermined angle in the all-optical fiber type Mahzender interferometer structure of claim 1 Optical fiber type Mahzander interferometer having a first optical coupler and a second optical coupler fabricated so that the optical fiber or cladding is larger than twice the diameter of the optical fiber or the optical fiber cladding All-fiber-type Mahzender interferometer using a UV-curable, heat-curing epoxy-based silicone as the main material of thermal expansion coefficient to reduce or increase stress in claim 2 The all-fiber type Mahzender interferometer, which is applied to contact the outer portion of the epoxy without fixing the optical fiber forming the interferometer by directly applying the epoxy position to the optical fiber of the interferometer on the upper or lower portion of the epoxy in claim 2 The all-optical fiber type Mahzander interferometer having a structure in which at least one epoxy-coated portion of the two interferometers in claim 2

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