JPS60243609A - Optical multiplexer/demultiplexer - Google Patents

Abstract

PURPOSE:To permit easy optical axis adjustment and reduction of man-hour for assembly and adjustment by covering the part between the optical paths formed of cylindrical rod lenses including filters and optical fibers with a transparent plastic resin having the refractive index equal to the refractive index of optical fibers. CONSTITUTION:Grooves 39, 42-46 similar to preliminarily designed optical axes are formed to a substrate 38 and respective transmission ports are set in prescribed positions. The fine adjustment to maximize the light intensity on the exit side is executed by moving V-groove holders 32 in the optical axis direction with the grooves 39, 42-46 as a guide. The adjustments for the transmission ports lambda1-lambda6 corresponding to respective wavelengths are executed. The assembly subjected to the optical axis adjustment in the above-mentioned manner is put together with the substrate 38 into a case and the transparent plastic having the refractive index substantially equal to the refractive index of the optical fibers 28 is packed therein and is cured to form the optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical multiplexer/demultiplexer that is essential for simultaneously transmitting a plurality of optical signals of different wavelengths to a single optical fiber.

[Background of the invention]

Recently, optical fiber communication systems are entering the stage of full-scale practical use as control systems in the fields of electric power, Φiron-copper, and chemical plants. An optical multiplexer/demultiplexer is one of the essential optical components in the configuration of the optical communication system mentioned above. Various types of optical multiplexer/demultiplexers have been proposed so far, such as a prism type and a diffraction grating type. However, the one shown in FIG. 1 has recently been developed as the mainstream. (%Kasho 55-25045
) In FIG. 1, 42 is a glass bulk, and 22 to 27 are bandpass filters using dielectric interference films, each having a different wavelength. 15-21 are glass spacers, 8-
14 is a rod-shaped lens for collimating the light of the optical fiber 1, and 9 to 14 are rod-shaped lenses for condensing light.

The operation of such an optical multiplexer/demultiplexer is to collimate the wavelength band λ1 to λ6 in the multiplexed optical fiber 1 with the rod-shaped lens 8, pass it through the glass spacer 15 and the glass bulk 42, and pass it through the filter 22. incident, only wavelengths λ are allowed to pass through, and other wavelengths are reflected. The remaining reflected light then passes through the glass bulk 42 and enters the filter 23. By repeating this operation, the remaining wavelengths λ, ˜λ, are sequentially extracted.

FIG. 2 shows the spectral characteristics of each wavelength extracted in this way. The half-value width for each wavelength largely depends on the spectral characteristics of each filter.

Next, in the optical multiplexing/demultiplexing/multiplexing circuit, the optical fiber 1
It is necessary to reduce the optical loss as much as possible before the emitted light enters the optical 2-eyeper 2. FIG. 6 shows the relationship between axis misalignment and optical loss when a Gl type optical fiber with a core diameter of 50 μm is used in the optical fiber transmission system. Similarly, the relationship between angular deviation and optical loss is shown in FIG. Although a rod-shaped lens is used to enlarge the light beam and reduce loss,
High precision is required, with an allowable axial misalignment of 8 μm and an angular deviation of 1 degree. Therefore, in order to meet this requirement, the component parts of the optical multiplexer/demultiplexer need to be highly accurate, and the glass bulk is required to have an angle of 4 μm/QM, necessitating ultra-precision processing. Also, in the assembly process of each part.

The optical axis must be adjusted for each boat, and an adhesive or the like is generally used to hold and fix the boat, which requires a lengthy assembly process. Therefore, the conventional optical multiplexer/demultiplexer has the drawback of being extremely expensive.

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art;
The object of the present invention is to provide an optical multiplexer/demultiplexer that achieves high performance and low cost.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention fixes an optical fiber, a rod-shaped lens, and an interference film filter on a holder such as an r-groove, and places a V on a substrate having a predetermined groove shape using the groove as a guide. Adjust the optical axis by sliding the groove holder. After completing the adjustment, fill the optical path with transparent plastic resin and harden the resin under predetermined conditions to form an optical multiplexer/demultiplexer. The key point of the invention is that the optical axis can be easily adjusted without requiring a glass spacer.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 5 to 10. Figure 5 shows one transmission line boat, with optical fibers 28
is held and fixed on the central axis of the fiber holder 29, which is a hollow cylindrical body. The interference film filter 5111t is attached to the end surface of a cylindrical glass body cut at a predetermined angle with a vapor deposition device (
(not shown). In addition, optical fiber 2
A rod lens 60 for collimating (focusing) the emitted light (incident light) from 8 is fixed to the V#I holder 32 together with the fiber holder 29 and the interference film filter 51 using an adhesive or a plate spring. has been done. Here, adhesive 5
FIG. 6 shows an example of the above-mentioned transmission line boat configuration using 2.

Similarly, a necessary number of interference film filters with different selection wavelengths are prepared, and a predetermined number of transmission line boats are created by the above-described procedure.

Next, a method for adjusting the optical axis between each transmission line boat will be described. First, holes 39, 42 to 46, which are similar to the optical axis designed in advance, are formed on the substrate 38, as shown in FIG.

The grooves 39, 42 to 46 can be formed by a conventional mechanical method or by forming the grooves 39, 42 to 46 on the substrate 38 of , set each of the above-mentioned transmission line boats at predetermined positions, move the V-groove holder 39 in the optical axis direction as shown in FIG. 9 using the grooves 59, 42 to 46 as guides, and adjust the light intensity on the output side. Make fine adjustments until it reaches its maximum. Similarly,
Transmission line boats (λ, to λ,) corresponding to each wavelength are adjusted. This operation will be explained in more detail with reference to FIG. Transmission line boats of λ, to λ are temporarily fixed at predetermined positions in the grooves 39, 42 to 46 using a substrate 38 having a predetermined groove shape. Here, λ propagating through the optical fiber
, ~λ6 are collimated by a rod lens. Next, using the transmission line boat f@59 as a guide, move the V#l holder in the optical axis direction, and finely move it to the position where the light intensity of wavelength λ is maximum among the light incident on the interference film filter 36. After the adjustment, the V-groove holder 37 is temporarily fixed to the substrate 68. Next, λ reflected by the interference film filter 36.

Regarding the transmission line boat for selecting λ from among the wavelengths of ~λ6, optical axis adjustment is performed for each of the above transmission line boats using the groove 44 as a guide. Do the following. In this way, the grooves 39, 42 to 46 of the substrate 58
By simply sliding the V#I holder 3751 using as a guide, it becomes possible to easily adjust the optical axis frame.

Next, the substrate 58 for which the optical axis adjustment has been completed is placed in the case 40, and as shown in FIG. Put each transmission line boat of λ, ~λ6 formed by the beam force 53 into a transparent plastic 54
to cause optical damage. Thereafter, a light path is formed by curing the transparent plastic 54 under predetermined conditions.

Here, the transparent plastic 54 is attached to the optical fiber 2.
It should be substantially equal to the refractive index of 8. The reason for this is to prevent reflection of light at the end face of the optical fiber 28, the rod lens 30, the interference film filter 61, and the end face. Further, it is desirable that the light transmittance is 98% or more. In addition, as for the above-mentioned transparent plastic, a room temperature curing type or a photo curing type is superior in terms of improving workability. As the room temperature curing plastic mentioned above, R
TV-type silicone rubber, epoxy cast gel, epoxy gel, etc. are suitable.
(manufactured by Tsuku Corporation) gave particularly good results.

Further, as photo-curing plastics, UV-curable acrylic and epoxy-based plastics were good, and N0A65 (manufactured by Norland) was particularly good in terms of fC%.

As described above, according to the present invention, good results as an optical multiplexer/demultiplexer were obtained with insertion loss <2.0 dB and crosstalk>=30 dB in the wavelength range of 0.7 to 13 μm.

〔Effect of the invention〕

According to the present invention, it is possible to extremely easily adjust the optical axis of an optical multiplexed signal using the r-groove holder and the groove on the substrate, and the number of assembly and adjustment steps, which was the main cause of high costs in the past, can be significantly reduced. (Conventional 5.0 hours/port → 0.5 hours/boat) Yes. Furthermore, the optical path through which the optical signal passes is made of transparent plastic.
By forming the optical multiplexer/demultiplexer with a solid material, parts such as high-precision glass bulk and glass spacers, which conventionally accounted for the major cost of parts, are no longer required.
1/10 or less).

[Brief explanation of the drawing]

Figure 1 is a plan view showing a conventional optical multiplexer/demultiplexer, Figure 2 is a characteristic diagram showing the spectral characteristics of the conventional optical multiplexer/demultiplexer, and Figures 3 and 4 are for optical multiplexer/demultiplexer set M. A characteristic diagram showing the relationship between accuracy and optical loss, Fig. 5 is a perspective view of a transmission line boat showing an embodiment of the present invention, Fig. 6 is a perspective view showing the assembled state of the transmission line boat, and Figure 7 is a The board is shown, (a) is a plan view, (A) is a side view, Fig. 8 is a plan view showing the assembled state of the optical multiplexer/demultiplexer, and Fig. 9 is a plan view.
The figure is an enlarged view of the main part of FIG. 8, and FIG. 10 is a front view showing the process of coating with transparent plastic resin. 1-7・Optical fiber 8 4...Cylindrical rod lens 1ζ~') 1. ,, -N spacer 22 to 27...Interference film filter 42...Glass bulk 28...Optical fin (29
...Fiber holder 30...Cylindrical lens 31.
...Interference film filter 32...r groove holder 6B...
Substrate 69...Groove 54...Transparent plastic patent attorney Akira Takahashi ) Closed 5 figure 2 6th figure t jZ 7th figure J ￥38 figure

Claims (1)

[Claims] t In an optical multiplexer/demultiplexer configured with a bandpass filter using a plurality of multilayer dielectric interference films, the optical path formed by the cylindrical rod lens including the filter and the optical fiber has a refractive index substantially equal to that of the optical fiber. An optical multiplexer/demultiplexer characterized in that the optical multiplexer/demultiplexer is coated with a transparent plastic resin having the same values.