JP2002296456A - Transmission/reception module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the optical position adjustment of individual optical components and to provide a small-sized, easy-to-assemble new structure by integrating the optical components in a transmission/reception module which is provided with a light emitting device, a light receiving device and an optical fiber for leading out and introducing optical signals and which transmits and receives optical signals of a plurality of wavelengths. SOLUTION: The tip of the optical fiber is housed in a transparent tube, the transparent tube is provided with an end face inclined to a surface perpendicular to the center axis, a transparent block is joined through a filter to the inclined end face and the filter is provided on the surface of the transparent tube emitting light introduced from the optical fiber and reflected on the inclined end face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication for transmitting and receiving optical signals, which has both a light-emitting element and a light-receiving element, and performs optical-to-optical conversion and optical-to-electrical conversion. Related to the transmission / reception module.

[0002]

2. Description of the Related Art An increase in information transmission capacity in a public communication network, a LAN, or the like accompanying the advancement of information and multimedia has become a serious problem. As means for solving this, various optical communication systems to which the optical transmission technology is applied have attracted attention, and optical networking has been rapidly spreading in recent years.

[0003] Among them, optical two-way communication in which two points are connected by one optical fiber to communicate with each other requires only one transmission path and does not take up space for a cable. is there.

In supporting these optical communication systems, various optical element modules mounted with a light emitting element and a light receiving element are the most basic components, and establishment of mass production technology for realizing cost reduction is an important issue. Has become.

FIG. 3 is a structural diagram of a transmission / reception module used for optical bidirectional communication in which transmission / reception is performed with two wavelengths of optical signals over one optical fiber.

[0006] A light emitting element 1 that emits transmission light of wavelength λ1 and transmission light of wavelength λ1 are transmitted through a transmission side condenser lens 2 to wavelength λ1.
The optical fiber 3 that guides one transmission light, and the reception light of the wavelength λ2, which has been reflected through the demultiplexing filter 4 having the reflected component with respect to the reception light of the wavelength λ2 that has passed through the optical fiber 3, are received. The side condensing lens 5 has a structure in which the light is guided to a light receiving element 6 having sensitivity to the received light having the wavelength λ2.

In addition, a filter 7 that transmits only the received light of wavelength λ2 is provided for the function of preventing light leaking from the light emitting element 1 and receiving light other than the received light of wavelength λ2 that has passed through the optical fiber 3. The filter 7 is provided between the receiving-side condenser lens 5 and the demultiplexing filter 4, and the filter 7 is particularly important when high-sensitivity reception is required (Japanese Patent Laid-Open No. 9-30466).
No. 6).

[0008]

However, the transmission / reception module having the conventional structure shown in FIG. 3 requires many optical components, and all the optical components need to be arranged at the optimum positions. Each of the optical components is attached to a metal fitting using an adhesive or the like, and after adjusting the positions of the respective metal fittings, the structure is fixed by laser welding or the like. There was a problem of complexity.

For example, in the above-described conventional structure, it is necessary to adjust the light emitting element 1 to an optimum position after the branching filter 4 and the transmission side condenser lens 2 are assembled. As a result, the transmission light of wavelength λ1 emitted from the light emitting element 1 is condensed by the transmission-side condensing lens 2 and forms an image at the optimum position after passing through the demultiplexing filter 4. By adjusting the position of the optical fiber 3 to this focusing position, it is possible to guide the optimum amount of light to the optical fiber 3.

Further, the filter 7 and the receiving-side condenser lens 5 need to be fixed at appropriate positions through which the received light of wavelength λ2 reflected by the demultiplexing filter 4 passes. As a result, the received light of wavelength λ2 transmitted through the optical fiber 3 is reflected by the demultiplexing filter 4, passes through the filter 7, and
The light is condensed by the receiving side condensing lens 5 to form an image at an optimum position. By adjusting the position of the light receiving element 6 to this light condensing position, it is possible to obtain an optimal light amount.

In order to perform these optical adjustments, the shape of the bracket to which each optical component is attached is complicated and requires high precision, and an interval for avoiding collision of the optical components during adjustment is also required. There was a limitation of becoming.

In particular, in order to dispose the components of the filter 7, it is necessary to make the optical system relatively long, and there is a problem that miniaturization is difficult.

An object of the present invention is to solve the above-mentioned problems of the conventional transmitting / receiving module.

[0014]

In order to solve the above-mentioned conventional problems, the present invention comprises a light emitting element, a light receiving element, and an optical fiber for deriving and introducing an optical signal. In the transmitting / receiving module for transmitting and receiving, the tip of the optical fiber is housed in a transparent tube, the transparent tube has an end surface inclined with respect to a plane perpendicular to the central axis, and a transparent block is joined to the inclined end surface via a filter. Further, a filter is provided on the surface of the transparent tube from which the light introduced from the optical fiber and reflected by the inclined end surface is emitted.

An antireflection film or a filter is provided on a surface of the transparent block facing the light emitting element.

[0016]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the portion of the optical fiber 8 from which the coating has been removed is fixed to a transparent tube 9, and the end face of the transparent tube 9 is polished at 45 degrees to a plane perpendicular to the central axis of the optical fiber 8. It is an end face 9a. The transparent block 11 is adhered and fixed to the inclined end surface 9a with an adhesive having the same refractive index as that of the transparent block 11 via a branching filter 10 that reflects light of wavelength λ4 and transmits light of wavelength λ3. The demultiplexing filter 10 is formed by coating the transparent block 11 or the transparent tube 9. The light introduced from the optical fiber 8 is reflected by the inclined end face 9a, and the surface of the transparent tube 9 from which the light is emitted is provided with a flat surface 12, and the filter 13 is coated.

The transparent tube 9 is bonded and fixed to a metal fitting 18. On the other hand, the light emitting element 15 which is resistance-welded to the metal fitting 19 and the transmission side condenser lens 16 which has a low melting point glass attached to the metal fitting 20.
Are adjusted to a position where the light emitted from the light emitting element 15 is led out to the optical fiber 8 via the transmission side lens 16, and is fixed to the fitting 18 by laser welding.

The metal fitting 18 has an opening at the position of the filter 13 of the transparent tube 9. The light receiving element 14 with the light-receiving side condenser lens, which is resistance-welded to the metal fitting 21, is introduced from the optical fiber 8, The position is adjusted so that the light reflected by 10 and passed through the filter 13 is incident, and laser-welded to the metal fitting 18.

Now, the wavelength λ introduced from the optical fiber 8 is
4 is transmitted through the transmission light of the wavelength λ3 on the 45 ° inclined end surface 9a and is reflected by the demultiplexing filter 10 that reflects the reception light of the wavelength λ4. The light is emitted from the plane 12 by changing the optical path vertically. This plane 1
2 is coated with a filter 13 that transmits the reception light of wavelength λ4 and reflects the transmission light of wavelength λ3.
3 has a function of preventing stray light from being transmitted. This makes it possible to accurately convert even a small optical signal on the receiving side into an electric signal without being affected by the transmitted light during simultaneous transmission and reception.

The transmission light having the wavelength λ3 is radiated from the light emitting element 15, is condensed by the transmission side condenser lens 16, and is introduced into the optical fiber 8 through the transparent block 11.

Here, by providing the transparent block 11 having the same refractive index as the core of the optical fiber, the transmission light of the wavelength λ3 from the light emitting element 15 can be transmitted from the light emitting element 15 without being affected by the 45 ° inclined end face 9a. The light can be led out through the condenser lens 16 without waste. Since bidirectional transmission and reception can be performed as described above, since the demultiplexing filter 10 is provided on the inclined end face 9a and the filter 13 is directly provided on the transparent tube 9, the size can be reduced and the assembly becomes easy.

FIG. 2 shows an enlarged view of the transmitting side of FIG.

Here, the surface 17 of the transparent block 11 facing the light-emitting element 15 is
By inclining the light condensed through the light source at an angle of 4 to 12 degrees with respect to the direction perpendicular to the optical axis, the reflected return light from the facing surface 17 is reduced, and the light emitting state of the light emitting element 15 becomes unstable. Can be prevented. Further, by coating the facing surface 17 with an anti-reflection film, the return light reflected by the facing surface 17 of the transmission light having the wavelength λ3 emitted from the light emitting element 15 is reduced, and the light emitting state is prevented from becoming unstable. You can also. In particular, shorten the optical path length on the light receiving element 14 side,
Dimensions can be reduced.

When used in a system that uses communication light other than the wavelength used in the transmission / reception module, the opposite surface 17 is coated with an interference film filter that transmits only the transmission light of wavelength λ3. Therefore, even if light of other wavelengths enters, it does not affect the light emitting state of the light emitting element 15.

As a material of the transparent tube 9 and the transparent block 11, a hard glass having a refractive index close to that of the core of the optical fiber 8 and easy to process, or a resin having no loss with respect to a used wavelength is used. As a material of the demultiplexing filter 10 and the filter 13, a dielectric multilayer film such as ZnS, CeO ₂ , ZrO ₂ or TiO ₂ is used.

[0027]

EXAMPLE A transmission / reception module shown in FIG. 1 of the present invention was experimentally manufactured.

The end face of the glass transparent tube 9 has a 45 ° inclined end face 9a with respect to a plane perpendicular to the central axis of the hole through which the optical fiber 8 passes. The transparent tube 9 has a flat surface 12 on a side surface facing the inclined end surface 9a, and has a wavelength of 1.5.
5 μm (λ4) light is transmitted, and the wavelength is 1.31 μm (λ
The filter 13 for reflecting the light of 3) is coated.

After the end of the optical fiber 8 of the single mode fiber is removed from the coating, the transparent tube 9 is adhered and fixed to the transparent tube 9 with an epoxy adhesive so that no step is formed along the inclined end surface 9a of the transparent tube 9. Polished. At this time, it is desirable to use an adhesive having a refractive index equivalent to that of the core and to sufficiently remove bubbles so as not to cause bubbles.

The inclined end face 9a has a wavelength of 1.31 μm (λ
A transparent block 11 on which a demultiplexing filter 10 that transmits light of 3) and reflects light having a wavelength of 1.55 μm (λ4) is deposited.
Is bonded and fixed using an epoxy adhesive.

At this time, the transparent block 11 and the epoxy adhesive for fixing the transparent block 11 have a refractive index equivalent to that of the core of the optical fiber 8.

The optical fiber 8 and the transparent tube 9 having the transparent block 11 are bonded and fixed to a metal fitting 18 using an epoxy-based adhesive, and the light emitting element 15 and the metal fitting 20 attached to the metal fitting 19 by resistance welding have a low melting point. The transmission-side condenser lens 16 attached with glass is adjusted to a position where the light emitted from the light emitting element 15 is led out to the optical fiber 8 via the transmission-side lens 16, and is laser-welded to the fitting 18. Fixed. The metal fittings 18, 19 and 20 are made of stainless steel having excellent weldability and rust prevention, and the light emitting element 15 has a wavelength of 1.31 μm.
Transmission side focusing lens 1 using Fabry-Perot laser
Reference numeral 6 used an aspheric lens. By using an aspherical lens, the influence of spherical aberration can be reduced and high coupling efficiency can be obtained.

As described above, the demultiplexing filter 10 is provided directly on the inclined end face 9a of the optical fiber 8, and the
Are integrated, the optical distance is very short, and it is possible to use a light receiving element with a ball lens having a short focusing position.

Further, with respect to the opening at the position of the plane 12 of the metal fitting 18, the light receiving element 14 with the light-receiving side condensing lens, which is resistance-welded to the metal fitting 21, is adjusted to a position where the received light from the optical fiber 8 can be introduced. And fixed by laser welding. The metal fitting 21 was also made of stainless steel having excellent weldability and rust prevention.

The number of parts, the number of assembling steps, and the dimensions of the transceiver module shown in FIG. 1 of the present invention and the transceiver module shown in FIG. 3 of the conventional example were compared.

[0036]

[Table 1]

From these results, the conventional transmitting / receiving module shown in FIG. 3 has 13 components and a housing size of 24 × 4.
In contrast to 13.5 × 8 mm, the present invention requires only 10 points, the dimensions are 24 × 9.5 × 8 mm, and the dimensions on the light receiving element 14 side can be reduced by 4 mm.

[0038]

According to the present invention, a light emitting element, a light receiving element,
And in the transmitting and receiving module having an optical fiber for deriving and introducing an optical signal, and transmitting and receiving optical signals of a plurality of wavelengths, the tip of the optical fiber is housed in a transparent tube, and the transparent tube is perpendicular to the central axis. It has an end face inclined to the surface, and a transparent block is joined to this inclined end face via a filter,
By providing a filter on the surface of the transparent tube from which the light reflected from the inclined end face is emitted from the optical fiber,
The number of parts and the number of assembling steps can be reduced, and the space can be reduced by reducing the space for the parts themselves and the space for the parts to be held.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a transmitting / receiving module of the present invention.

FIG. 2 is an enlarged sectional view of the transmitting side of the transmitting / receiving module of the present invention.

FIG. 3 is a cross-sectional view showing a conventional transmitting / receiving module.

[Explanation of symbols]

 8: Optical fiber 9: Transparent tube 9a: Inclined end face 10: Demultiplexing filter 11: Transparent block 12: Flat 13: Filter 14: Light receiving element 15: Light emitting element 16: Transmitting condenser lens 17: Opposing surface 18: Metal fitting 19 : Metal fitting 20: Metal fitting 21: Metal fitting λ1: Wavelength λ2: Wavelength λ3: Wavelength λ4: Wavelength

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/28 H01L 31/02 D 5K002 10/26 H04B 9/00 Y 10/14 10/04 10/06 F-term (reference) 2H037 AA01 BA03 BA12 CA32 CA37 DA03 DA04 DA05 DA35 5F041 EE03 EE04 EE06 EE22 EE23 FF14 5F073 BA01 BA02 EA26 FA06 FA07 FA30 5F088 BA03 BA16 BB01 EA09 JA12 JA13 JA14 5F007 A0101

Claims (2)

[Claims] A light-emitting element, a light-receiving element, and derivation of an optical signal;
In a transmitting / receiving module having an optical fiber for introduction and transmitting and receiving optical signals of a plurality of wavelengths, the tip of the optical fiber is housed in a transparent tube, and the transparent tube is inclined with respect to a plane perpendicular to the central axis. A transparent block having an end face, a transparent block bonded to the inclined end face via a filter, and a filter provided on a surface of a transparent tube from which the light introduced from the optical fiber and reflected by the inclined end face is emitted. module. 2. The transmission / reception module according to claim 1, wherein an anti-reflection film or a filter is provided on a surface of the transparent block facing the light emitting element.