KR100720790B1 - Optical module for bidirectional communication improved incident angle precision of ferruled optical fiber - Google Patents

Abstract

The present invention relates to a bidirectional optical module for transmitting a wavelength division optical signal, comprising: a light emitting element and a light receiving element for transmitting and receiving an optical signal; A wavelength separation filter disposed to be inclined to correspond to both the light emitting element and the light receiving element so as to selectively separate the transmission wavelength and the reception wavelength; And an APC type end that is aligned on the optical axis passing through any one of the light emitting element or the light receiving element and the wavelength separation filter to face the wavelength separation filter, and is inclinedly processed, Disclosed is a bidirectional optical module comprising a ferrule optical fiber in which the ferrule portion is inclined with respect to the optical axis to correct an error.

Ferrule Fiber, APC, Bidirectional Optical Module, CWDM

Description

Optical module for bidirectional communication improved incident angle precision of ferruled optical fiber

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a perspective view showing the appearance of a general bidirectional optical module.

2 is a configuration diagram of FIG. 1.

3 is a block diagram of a bidirectional optical module according to a preferred embodiment of the present invention.

4 is a longitudinal sectional view showing a coupling relationship between a filter fixing part and a ferrule fixing part provided according to the present invention;

FIG. 5 is a perspective view showing an appearance of the ferrule fixing part of FIG. 4. FIG.

FIG. 6 is a cross-sectional view showing an arrangement state of the ferrule optical fiber in FIG. 4. FIG.

Figure 7 is a system configuration for measuring the wavelength characteristic of the bidirectional optical module according to the present invention.

8 is a graph showing the wavelength characteristics of the bidirectional optical module according to the present invention for each position of the APC.

<Description of main reference numerals in the drawings>

100 ... light emitting element 101 ... light emitting element

Ferrule Optical Fiber 103 Wavelength Separation Filter

104 ... filter holder 105 ... ferrule holder

The present invention relates to a bidirectional optical module for transmitting an optical signal of a wavelength division method, and more particularly, to a bidirectional optical module having an optical fiber arrangement structure for correcting an incident angle error of a ferrule optical fiber with respect to a wavelength separation filter.

Conventional optical transmission lines have mainly used 1310nm band with excellent dispersion characteristics and 1550nm band with excellent optical loss characteristics, but in recent years, for example, CWDM (Coarse Wavelength) that can utilize 16 channels at 20nm intervals from 1300nm to 1600nm band, for example. Division-type transmission technology has reached a level capable of providing high quality and large capacity transmission services.

1 and 2 illustrate the configuration of a bidirectional module supporting transmission and reception of optical signals in such a CWDM system.

Referring to FIG. 1, a laser diode 10 for transmitting an optical signal and a photodiode 11 for receiving an optical signal are spaced apart from each other in the bidirectional module, and the laser diode 10 and the photodiode 11 are spaced apart from each other. ), The wavelength separation filter 13 is disposed at an angle of 45 °. In addition, an optical fiber (hereinafter referred to as a ferrule optical fiber) 12 having ferrules coupled thereto is disposed on one surface of the wavelength separation filter 13 and output from the laser diode 10 and then transmitted through the wavelength separation filter 13. While transmitting a signal, an optical signal to be received by the photodiode 11, which is received from the outside, is incident on the reflecting surface of the wavelength separation filter 13.

Here, in particular, the ferrule optical fiber 12 generally has an APC (Angled polished connector) 12a structure that is processed to have a predetermined inclination angle in order to prevent the optical signal from being returned by the light reflection. Therefore, although the optical axis O of the wavelength separation filter 13 and the ferrule optical fiber 12 coincide and the wavelength separation filter 13 is inclined by 45 ° with respect to the optical axis O, the APC 12a is typically used. Considering that the inclination angle of the optical fiber is processed to about 8 °, and the refractive index difference in the optical fiber and the refractive index difference in free space, the light output from the APC 12a of the ferrule optical fiber 12 has an error of about 4 ° (δ). Is added to enter the wavelength separation filter 13 at an angle inclined by about 49 ° with respect to the filter surface.

This error is not a problem when the wavelength interval is large enough, such as the optical transmission of the WDM method using optical wavelengths of 1550 nm and 1310 nm, but when the wavelength interval is dense like the CWDM method, the characteristics of the filter may vary depending on the input angle. The problem arises in that it becomes sensitive and cannot achieve the desired wavelength separation characteristics.

In addition, since the conventional bidirectional optical module is generally manufactured by pressing and bonding the ferrule optical fiber 12 to the filter fixing part (not shown), it is difficult to correct the junction tolerance because the incident angle formed by the input light with the filter is fixed. There is a vulnerability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a bidirectional optical module having an arrangement structure capable of correcting an incident angle error caused by an end APC structure of a ferrule optical fiber.

Another object of the present invention is to provide a bidirectional optical module having a ferrule fixing structure that can conveniently perform the angle of incidence correction and fixation of the ferrule optical fiber with respect to the wavelength separation filter.

In order to achieve the above object, a bidirectional optical module according to a preferred embodiment of the present invention includes a light emitting element and a light receiving element for transmitting and receiving an optical signal; A wavelength separation filter disposed to be inclined to correspond to both the light emitting element and the light receiving element so as to selectively separate the transmission wavelength and the reception wavelength; And an APC type end that is aligned on the optical axis passing through any one of the light emitting element or the light receiving element and the wavelength separation filter to face the wavelength separation filter, and is inclinedly processed, And a ferrule optical fiber in which the ferrule portion is inclined with respect to the optical axis so as to correct an error.

Preferably, the wavelength separation filter is disposed to form 45 ° with respect to the optical axis, and the ferrule optical fiber is inclined at an angle of -δ with respect to the optical axis so as to correct that the incident angle of the filter surface becomes 45 ° + δ due to the APC structure. do.

The present invention includes: a filter fixing part for supporting the wavelength separation filter and having a mounting hole formed at the center thereof on the optical axis; And a ferrule fixing part inserted into the mounting hole and configured to allow the coupling hole into which the ferrule optical fiber is inserted to be inclined by δ with respect to the center of the mounting hole.

In consideration of the APC structure of the ferrule optical fiber, the inclination angle δ of the ferrule with respect to the optical axis is preferably 2 ° to 6 °.

As the wavelength separation filter, a filter for separating CWDM wavelengths of 1510 nm and 1570 nm bands is preferably used.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

 3 shows a configuration of a bidirectional optical module according to a preferred embodiment of the present invention.

Referring to FIG. 3, the bidirectional optical module according to an exemplary embodiment of the present invention includes a light emitting device 100 and a light receiving device 101, and a wavelength separation filter 103 disposed to be inclined to separate the light wavelength for transmitting and the light wavelength for receiving. And a ferrule optical fiber 102 disposed corresponding to one surface of the wavelength separation filter 103, a filter fixing part (see 104 in FIG. 4) for fixing the wavelength separation filter 103, and a wavelength separation filter 103. And a ferrule fixing portion (see 105 in FIG. 4) which can secure the ferrule optical fiber 102 to be inclined to correct an incidence angle error of the ferrule optical fiber 102 with respect to.

As the light emitting device 100 and the light receiving device 101 spaced apart from each other, for example, a laser diode and a photodiode capable of transmitting and receiving CWDM light wavelengths in the 1510 nm or 1570 nm band are preferably employed.

The wavelength separation filter 103 is disposed on the optical axis O at a point where the light emitting device 100 and the light receiving device 101 vertically meet each other so that both surfaces of the light emitting device 100 and the light receiving device 101 are equally aligned. It is arranged to incline 45 ° with respect to. As the wavelength separation filter 103, a general thin film filter manufactured by depositing a multilayer dielectric thin film may be employed. In addition, in consideration of the optical transmission in the CWDM method, it is preferable that the separation and blocking characteristics of the wavelength separation filter 103 differ by more than 15 dB from the pass band and the separation band, and the wavelength shift of 10 nm with respect to the change of the input angle of 1 °. It is preferable that a filter having a characteristic is employed.

The wavelength separation filter 103 is supported by the filter fixing part 104 to maintain its fixed state. Here, the filter fixing part 104 has a mounting hole (not shown) into which the ferrule fixing part 105 can be fitted, and any one of the light emitting device 100 or the light receiving device 101 and the wavelength separation filter ( The optical axis O passing through 103 is aligned to be centered in the mounting fixture.

On one side of the wavelength separation filter 103, a ferrule optical fiber 102 having an end of the APC 102a structure is fixed to the ferrule fixing part 105 so as to be positioned on the optical axis O. Here, the ferrule optical fiber 102, the light output from the ferrule optical fiber 102 is incident on the filter surface of the wavelength separation filter 103 at the filter surface incident angle of 45 ° + δ by the APC 102a, refractive index difference, etc. In consideration of this, it is disposed inclined by -δ with respect to the optical axis O. That is, the APC 102a structure is typically processed to have an inclination angle of 8 °, and the refractive index difference between the optical fiber and the air, the processing tolerance of the ferrule fixing portion 105, the processing tolerance of the filter fixing portion 104, and the bonding tolerance during packaging. For example, when the error δ is 4 °, the ferrule optical fiber 202 is disposed to be inclined by 4 ° in the direction opposite to the error angle with respect to the optical axis O.

For the arrangement as described above, the ferrule fixing portion 105 has a cylindrical body formed with a coupling hole 106 into which the ferrule portion of the ferrule optical fiber 102 can be inserted, as shown in FIG. 5. Here, the outer shape of the body of the ferrule fixing portion 105 may be formed of a predetermined polygon.

The coupler 106 of the ferrule fixing part 105 is formed to be inclined by δ with respect to the central axis C of the cylindrical body. Here, δ is set in the range of 2 ° to 6 ° in consideration of the fact that the APC 102a of the ferrule optical fiber 102 has an inclination angle of 8 ° as described above, and the refractive index difference and various processing tolerances. It is preferable to set it to 4 degrees more precisely.

According to the above configuration, when the ferrule fixing part 105 is inserted into the mounting hole of the filter fixing part 104 and then the ferrule fixing part 105 is rotated and adjusted, the structure of the APC 102a of the ferrule optical fiber 102 is adjusted. The error δ can be corrected, and after the error is corrected, the filter is fixed by joining the filter fixing part 104 and the ferrule fixing part 105. 6 shows a coupling relationship between the ferrule optical fiber 102, the ferrule fixing part 105, and the filter fixing part 104 provided with the core 102a and the clad 102b.

FIG. 7 shows a measurement system configuration for measuring filter characteristics according to the alignment direction of the ferrule optical fiber 102 with respect to the wavelength separation filter 103. Referring to the drawings, the measurement system includes a tunable laser 200 capable of adjusting the output wavelength, and a bidirectional optical module having the arrangement of the wavelength separation filter 103 and the ferrule optical fiber 102 as described above. 201, a detection cell 202 for photodetection, an optical power meter 203, and the like. According to this measuring system, the angle of incidence of the laser light input from the ferrule optical fiber 102 to the wavelength separation filter 103 can be adjusted by rotating the ferrule fixing part 105 relative to the filter fixing part 104, and the incident angle change By measuring the filter characteristics according to the quantitative error can be corrected.

FIG. 8 is a graph illustrating measurement results of wavelength characteristics of the bidirectional optical module provided by the measurement system of FIG. 7. In the drawing, region I represents a wavelength band reflected by the wavelength separation filter 103 and input to the light receiving element 101, and region II represents a wavelength band output from the light emitting element 100 and transmitted through the wavelength separation filter 103. Indicates. In addition, graphs A to D show transmission characteristics for each wavelength band corresponding to the change in the incident angle as the ferrule fixing part 105 is rotated by 90 degrees.

 Referring to FIG. 8, it can be seen that there is a wavelength shift of 5 nm with respect to the incident angle change of 1 ° as the ferrule fixing part 105 is rotated. Therefore, the position of the ferrule optical fiber 102 can be adjusted to compensate for errors caused by the APC 102a structure or the like while monitoring the wavelength characteristic through the optical power meter 203 of the measurement system, and after the desired wavelength characteristic is secured When the ferrule fixing part 105 and the filter fixing part 104 are bonded to each other and the light emitting device 100 and the light receiving device 101 are aligned and bonded to each other based on the wavelength separation filter 103, the wavelength separation filter 103 is bonded to each other. A bidirectional module for CWDM optical transmission is fabricated that allows light incidence to be made exactly 45 ° with respect to the filter surface.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

The present invention can be used in a CWDM transmission system having a dense wavelength spacing of about 20 nm since the incident angle error generated in the wavelength separation filter due to the APC structure of the optical fiber can be corrected.

In addition, it is possible to increase the accuracy of the incident angle correction by performing the correction operation using the ferrule fixing portion provided for the incident angle correction, and the workability is excellent because the ferrule fixing portion is rotated to the optimum direction and then fixed. There is this.

Claims (5)

In the bidirectional optical module for wavelength division optical signal transmission, Light emitting device and light receiving device for transmitting and receiving the optical signal; A wavelength separation filter disposed to be inclined to correspond to both the light emitting element and the light receiving element so as to selectively separate the transmission wavelength and the reception wavelength; And An error in the filter plane incident angle due to the APC structure, which has an end of the APC type, which is aligned on the optical axis passing through either the light emitting device or the light receiving device and the wavelength separation filter, is opposite to the wavelength separation filter, and is inclinedly processed. And a ferrule optical fiber in which the ferrule portion is inclined with respect to the optical axis so as to correct the correction. The method of claim 1, The wavelength separation filter is disposed to form 45 ° with respect to the optical axis, And the ferrule portion of the ferrule optical fiber is inclined at an angle of -δ with respect to the optical axis so as to compensate that the incidence angle of the filter surface becomes 45 ° + δ due to the APC structure. The method of claim 2, A filter fixing part which supports the wavelength separation filter and has a mounting hole formed at the center thereof in the optical axis; And And a ferrule fixing part fitted to the mounting hole, the coupling hole into which the ferrule optical fiber can be inserted is inclined by δ with respect to the center of the mounting hole. The method of claim 3, Bidirectional optical module, characterized in that the inclination angle δ of the ferrule with respect to the optical axis is 2 ° ~ 6 °. The method of claim 1, The wavelength separation filter is a bidirectional optical module, characterized in that for separating the CWDM wavelength of 1510nm and 1570nm band.

Images