JPH04286376A - Optical module - Google Patents

Abstract

PURPOSE:To enable a two-way light transmission module to be miniaturized. CONSTITUTION:An LD element 11 and a PD element 12 are fixed inside a package 14. The fiber ends 18 and 19 of a fiber coupler 21 are fixed to a fiber terminal retainer 20. The package 14, lenses 16 and 17, the fiber terminal retainer 20, and the fiber coupler 21 are aligned with each other in optical axis and fixed inside a holder 22 so as to enable the LD 11 and the fiber 18 and the fiber 19 and the PD 12 to be optically coupled together.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication module, and more particularly to an optical module in which light emitting and light receiving elements are integrated.

0002

2. Description of the Related Art With the development of ISDN in the field of public communication networks, it is expected that large-capacity transmission of image information will be required not only to trunk lines but also to terminal subscriber lines. For such high-speed, large-capacity transmission, transmission using conventional metallic cables is not sufficient, and it is considered essential to implement an optical subscriber system by introducing optical transmission technology. One of the methods for realizing this optical subscriber system is the same wavelength bidirectional transmission method. This provides bidirectional transmission over a single optical fiber between the station and the subscriber terminal. FIG. 4 shows an example of a conventional transmitting/receiving optical module used in the same wavelength bidirectional transmission system. This transmitting/receiving optical module has a transmitting semiconductor laser module 41, a receiving photodiode module 42, and a pigtail fiber connected to the transmitting semiconductor laser module 41 and receiving photodiode module 42 through connectors 44 and 45, respectively. Fiber fusion type 3
It consists of a dB coupler 43. The transmission signal 1 converted into light by the semiconductor laser module 41 is sent to the transmission line through the 3 dB coupler 43. On the other hand, the received signal 2 arriving from the transmission path is split into two by a 3 dB coupler 43, and one of them is converted into an electrical signal by a receiving photodiode module 42.

0003

Problems to be Solved by the Invention In an optical subscriber system, one end of an optical terminal is placed on each subscriber's side. Therefore, optical modules are required to be downsized so that they can be accommodated in the same size as conventional metallic cable terminals, and to have environmental resistance and impact resistance that allow stable operation under various environments. Furthermore, on the central office side, the number of terminals in subscriber systems increases enormously compared to trunk systems, so there is a need for smaller optical modules. Conventional transmitter/receiver optical modules combine optical components with a single function, so the size inevitably increases because the semiconductor laser, photodiode, and coupler must each have environmental resistance and strength. It is also necessary to provide extra space to accommodate the pigtail fibers that connect the optical components. Therefore, it is difficult to achieve the miniaturization required for optical subscriber systems with conventional transmitting/receiving optical modules that combine individual optical components in this way. An object of the present invention is to provide a compact and environmentally resistant bidirectional transmission module in place of the above-mentioned conventional bidirectional transmission optical module.

0004

[Means for Solving the Problems] According to the present invention, there is provided a fiber type coupler element for optically coupling a pair of optical fibers, a fiber terminal holder having two parallel fiber insertion holes, and a pair of optical fibers. lenses, semiconductor laser elements,
and a photodiode element, each end of the pair of optical fibers is inserted into the insertion hole and fixed to the fiber terminal holder, and one of the ends is connected to the pair of optical lenses. The fiber-type coupler element is optically coupled to the semiconductor laser element through one of the ends thereof, and the other end thereof is optically coupled to the semiconductor photodiode element through the other of the pair of optical lenses. , an optical module is obtained, wherein the fiber end holder, the pair of optical lenses, the semiconductor laser element, and the photodiode element are housed in the same protective container.

[0005]

[Function] In the present invention, the semiconductor laser, photodiode, and fiber coupler that constitute the module are housed in the same container and are protected as one unit, so there is no need to individually reinforce their environmental resistance and strength. Similarly, no extra length of optical fiber is required to connect the components. Furthermore, since the semiconductor laser element and photodiode element are mounted inside the same sealing structure, the width of the module, which would be limited by the outer diameter of the package if the elements were individually sealed, can be significantly reduced. Therefore, it is possible to obtain an optical module for bidirectional transmission that is small in size and has environmental resistance.

[0006]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. In FIG. 1, a semiconductor laser 11 (hereinafter referred to as LD) and a PIN photodiode 12 (hereinafter referred to as PD) are mounted on the same stem 13. Figure 2 shows an example of its mounting structure. The LD 11 is fixed to the top surface of the stem 13 in order to emit light from the end surface 24 of the chip, and the PD 12 is fixed to the side surface of the stem 13 because the light receiving surface 25 is on the chip surface. The LD 11 and the PD 12 are electrically connected to bonding pads 26 and 27 provided on the stem 13, respectively, using bonding wires 28 and 29. Here, the LD 11 and the PD 12 are electrically insulated to prevent crosstalk. LD11 and P
The center distance from D12 is set to about 0.5 mm to 2 mm (hereinafter, this distance will be referred to as L). The stem 13 to which the LD 11 and PD 12 are fixed is housed in a package 14 and sealed. Referring again to FIG. 1, the lenses 16 and 17 provide optical coupling between the LD 11 and the output fiber 18, and between the input fiber 19 and the PD 12, respectively. Similar to the distance between LD11 and PD12, lenses 16 and 1
The center spacing of 7 is L. The output fiber 18 and the input fiber 19 are both fixed by a fiber end holder 20. Figures 3(a) and 3(b) show the fiber terminal structure. In the fiber terminal holder 20, insertion holes 31 and 32 having an inner diameter slightly larger than the outer diameter of the fiber are provided with a center spacing L, into which the fibers 18 and 19 are inserted and fixed. The tip of the fiber terminal holder 20 is optically polished obliquely at an angle of 3 to 7 degrees in order to reduce reflected and returned light. Further, the fibers 18 and 19 are fused and stretched before the terminal holder 20, and the fiber fused type 3dB coupler 2
1 is formed. One end of the fused fiber is connected to a transmission line, and the other end is terminated with anti-reflection treatment. the fiber terminal holder 20 and package 14;
Lenses 16, 17, and 3dB coupler 21 are each L.
The optical axis of the holder 22 is adjusted so that optical coupling can be made from D11 to fiber 18 and from fiber 19 to PD12.
, 23. In Figure 1, the input signal causes
The transmitted signal light 1 modulated by D11 is narrowed down by a lens 16 and enters a fiber 18, where it is passed through a 3dB coupler 21.
is sent to the transmission line through. Further, the received signal light 2 that has arrived from the transmission path is split into two by a 3 dB coupler 21, and then exits from the fiber 19, enters the PD 12 via the lens 17, and is converted into an output electrical signal. Received signal light 2 is 3d
The light is split into two by the B coupler 21, and is also incident on the LD 11 through the fiber 18. However, the received signal light 2 is significantly attenuated in the transmission path and is weaker than the LD output light.
Since the transmission speed of optical subscriber system transmission is at most 100 Mb/s, the influence of the incidence of the received signal light 2 on the modulation characteristics of the LD 11 can be ignored. In the configuration according to this embodiment, L
Environmental resistance of D11, PD12, 3bB coupler 21,
Since strength is ensured by the integrated holder, there is no need to individually reinforce each component. Since the 3 dB coupler 21 and the input and output ends of the optical fibers 18 and 19 are integrated, no extra length of the fiber is required. LD11,
Since the PDs 12 are fixed to the same stem 13, the width, which was limited by the outer diameter of the package, can be reduced, and a module that is much smaller than the conventional one can be realized. Although an example in which the stem 13 is housed and sealed within the package 14 has been described above, a similar effect can be obtained with a structure in which the stem 13 is sealed inside the holder 22 in the state of a chip carrier. Further, although optical coupling is performed using two lenses 16 and 17, the same effect can be obtained even when using an array lens that integrates the lenses, or when using a fiber laminated coupler as the 3 dB coupler 21. . Furthermore, by using a fiber type wavelength multiplexing/demultiplexing coupler instead of the 3 dB coupler 21, a similarly compact optical module for wavelength multiplexing and bidirectional transmission can be obtained.

[0007]

As described above, according to the present invention, it is possible to realize a transmitter/receiver module for bidirectional transmission of the same wavelength that is much smaller than the conventional one. Furthermore, by mounting the LD and PD in the same sealing structure and integrating the input and output fiber ends, the optical axis adjustment, fixing process, and optical polishing process of the fiber end face, which were previously required twice, can be reduced to one time each. The effect of reducing manufacturing costs can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a mounting structure of an LD element and a PD element.

[Fig. 3] (a) is a front view showing the fiber terminal structure, (b)
) is a plan view.

FIG. 4 is a diagram showing a configuration of a conventional bidirectional transmission transmitting/receiving module.

[Explanation of symbols]

1 Transmission signal light 2 Reception signal light 11 LD element 12 PD element 13 Stem 14 Packages 16, 17 Lenses 18, 19 Optical fiber 20 Fiber terminal holder 21, 43 Fiber coupler 22, 23
Holder 24 LD light emitting surface 25 PD light receiving surface 26, 27 Bonding pads 28, 29
Bonding wires 31, 32 Fiber insertion hole 41 LD module 42 PD module 44, 45 Connector

Claims (1)

[Claims] Claim 1: A fiber type coupler element that optically couples a pair of optical fibers, a fiber terminal holder in which two parallel fiber insertion holes are formed, a pair of optical lenses, a semiconductor laser element, and a photodiode element. each end of the pair of optical fibers is inserted into the insertion hole and fixed to the fiber terminal holder, and one of the ends is inserted through one of the pair of optical lenses. and the other of the end portions is optically coupled to the semiconductor photodiode element via the other of the pair of optical lenses, the fiber type coupler element and the fiber terminal. An optical module characterized in that a holder, the pair of optical lenses, the semiconductor laser element, and the photodiode element are housed in the same protective container.