JPS595225A - Optical demultiplexer - Google Patents

Abstract

PURPOSE:To decrease the crosstalk among spectra of transmitted plural different light and the quantity of near end leakage, by providing an optical fiber of which both ends are adhered to the end face of a near parabolic rod lens on the side opposite from a mirror. CONSTITUTION:The light having spectral components S1, S2 transmitted in an optical fiber 12 is made incident to a lens 18. The components S1 is reflected by a filter 16 and is made incident to the end 13A of an optical fiber 13. Said light is made incident again to the lens 18 from an end 13B. The incident light is reflected again by the filter 16 to enter an optial fiber 14, from which the light is outputted. On the other hand, the light of the component S2 transmits the filter 16, is reflected by a mirror 17, again transmits the filter 16 to enter an optical fiber 15 and is outputted from said fiber. Sine the crosstalk that the component S1 leaks to the output part of S2 is the quantity of the light transmitting the filter 16 twice, the crosstalk is reduced to a relatively small level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical demultiplexer that demultiplexes light having a plurality of different spectra transmitted through an optical fiber in an optical wavelength transmission system, and which demultiplexes light having a plurality of different spectra into individual spectra. The purpose of this is to reduce the amount of crosstalk or near-end leakage between the two.

FIG. 1 shows an example of a conventional optical demultiplexer for two-wave demultiplexing. In FIG. 1, reference numeral 1 denotes an input optical fiber, and light having two different spectral components S1(λ) and 82(λ) whose base portions intersect as shown in FIG. (spectral components are shown as 8 and 9 in FIG. 2) are transmitted. 2 and 3 are optical fibers for outputting different spectra. 4 is a focusing Rondo lens (hereinafter simply referred to as a lens) having a period length of A, and a conductive material interference film filter (hereinafter simply referred to as a filter) 10A having a transmittance characteristic of 10B shown in FIG. 2 is deposited on one end face. Further, a mirror 6 is bonded to this end face at a certain angle. Further, the input/output optical fibers 1, 2.degree. 3 are bonded on the same straight line to the other end surface of this lens 4. Reference numeral 6 denotes a cut filter consisting of two lenses and a filter 11 having a transmittance characteristic of 11B shown in FIG. An optical fiber 7 for output after passing through this cut filter 6 is bonded.

Next, the operation of the above conventional example will be explained. In FIG. 1, the output light S+(λ
), S2(λ) enters the lens 4, St(λ) is reflected according to the transmittance 10B of the filter 10, and the reflected spectrum enters the output fiber 2.

On the other hand, 82(λ) is transmitted according to the transmittance 10B of 10 filters, and the transmission spectrum is as follows after exiting the lens 4:
The light is reflected by the mirror 6, enters the lens 4 again, passes through 10 filters, and then enters the output fiber 3. In the above demultiplexing mode, the crosstalk (hereinafter referred to as C1) leaking from S+(λ) to the output section of 82(λ) is
) The amount of the spectrum component that is transmitted without being reflected by the filter 10A is reflected by the mirror 6 and transmitted again without being reflected by the 10 filters, that is, the amount that is transmitted through the filter twice, so it is relatively small. On the other hand, 32(λ) is 8+
The crosstalk (hereinafter referred to as C2) leaking to the output section of (λ) is a spectral component that is reflected without passing through the 82 (λ) filter 10m, that is, it is a single reflection component, so it is larger than C1. . Therefore, in this optical demultiplexer, 11
This value of 02 is further reduced by the cut filter 6 having 11 filters exhibiting the transmittance characteristic of B.

However, the conventional example described above has a drawback in that a lens 6 and a filter 11 must be added in order to reduce the amount of crosstalk C2.

The present invention eliminates the drawbacks of the above-mentioned conventional example, and one embodiment of the present invention will be described below with reference to FIG. 3.

In FIG. 3, reference numeral 18 is a lens similar to the lens 4 of the conventional example, and this lens 18 has a filter 16 deposited on one end face, similar to the filter 1om of the conventional example, and further has a filter 16 deposited on one end face. Similar to the conventional example, the mirror 17
are glued at a certain angle. 12 to 16 are optical fibers, and the optical fiber 13 has both ends 12, 14 .
One side of the optical fiber 15 is bonded to the end surface of the lens 18 on the opposite side to the mirror 17 in the same straight line.

Next, the operation of the above embodiment will be explained with reference to FIG. In FIG. 3, the spectral component S1 (λ) shown in FIG. 2 is transmitted through the optical fiber 12.

The light having S2(λ) is incident on the lens 18, and 81(λ) is the characteristic 10B of the filter 16 as in the optical demultiplexer.
Accordingly, #λ is reflected, and the reflected spectral component enters the optical fiber 13 located at 13mm, and the reflected spectral component enters the optical fiber 13 located at 13B of the lens 18.
The light enters the lens 18 again from the position . The incident light is again reflected by the filter 16, and the reflected spectral components are incident on the optical fiber 14 and output. That is, the signal is output by being reflected by the filter twice. On the other hand, the light of 82 (λ) is almost transmitted through the filter 16 similarly to the optical demultiplexer,
It is reflected by the mirror 17 and almost passes through the filter 16 again,
The light enters the optical fiber 16 and is output.

This embodiment has the advantage that by operating the same filter again for the light that has been output, one filter and two lenses can be omitted compared to the conventional example, and the same amount of crosstalk can be obtained.

4 to 6 show an optical demultiplexer according to a second embodiment of the present invention.

In FIGS. 4 to 6, 19mm and 19B are lenses similar to the lens 4 of the conventional example, and 24 is a filter having the characteristics of 10B shown in FIG. The lens 1 is then deposited on that surface.
9B is glued. 20 to 23 are optical fibers, the optical fiber 21 has both ends connected to the end surface of the lens 1eA, the optical fiber 20.22 has one side connected to the end surface of the lens 1eA, and the optical fiber 23 has its ends connected to the lens 19B.
are glued to the end faces of each. Further, the bonding position 26 of the optical fiber 20 and the bonding position 26 on one side of the optical fiber 210,
The bonding position 28 of the optical fiber 22 and the other side bonding position 27 of the optical fiber 21 are bonded at approximately symmetrical positions with respect to the axis of the lens 19A, respectively.

Next, the operation of the second embodiment will be explained with reference to FIGS. 4 to 6. In FIGS. 4 to 6, the optical fiber 20
The light having two different spectral components S1(λ) and S2(λ) shown in FIG.
) is almost reflected and enters the optical fiber 21 at the position 26. The incident light enters the lens 19 at the position 27, is reflected again according to the characteristics of the filter 24, enters the optical fiber 22 at the position 28, and is output. That is, it is output after being reflected twice. On the other hand, 82(λ) is transmitted through the filter 24 according to the characteristic 10B of the filter 24, enters the lens 19B, and is outputted by the optical fiber 23.

In this embodiment, the cut filter is constructed by arranging the input fiber bonding position, the once output fiber position, the position where the fiber is bonded to the lens again, and the device consisting of the lens again on the same circumference. The amount of crosstalk can be reduced without using a
By bonding the optical fiber at a position corresponding to the bonding position, there is an advantage that the amount of crosstalk can be reduced as necessary.

The present invention has the above-mentioned configuration, and according to the present invention, the following effects can be obtained.

(a) Since a desired amount of crosstalk can be obtained by transmitting or reflecting through the same filter, a cut filter consisting of a lens and a filter can be eliminated.

(b) Since the filter can be operated multiple times, there is an advantage that considerably small losstalk can be obtained.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional two-wave optical demultiplexer, and Figure 2 is a front view of a conventional two-wave optical demultiplexer.
Figure 3 is a front view of an optical demultiplexer according to an embodiment of the present invention, and Figure 4 is a diagram showing the spectral characteristics of the filter used in the figure and the spectra of two different transmitted lights. FIG. 5 is a front view of the optical demultiplexer of the second embodiment, FIG. 5 is a bottom view thereof, and FIG. 6 is a side view thereof. 12+ 13.14+ 16...Optical fiber, 16...Filter, 17...Mirror, 18...Lens, 1e A+ 19 B
-...-Lens, 20, 21, 22゜23...
・Optical fiber, 24...filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 U L 1 C 5 Figure 3

Claims (1)

[Claims] (1) A first device that transmits light having a plurality of different spectra.
an optical fiber, a focusing rod lens through which the light transmitted through the first optical fiber enters from one end surface, a dielectric interference film filter deposited on the other end surface of the focusing rod lens, and a dielectric interference film filter deposited on the other end surface of the focusing rod lens. a second optical fiber through which the reflected spectrum component reflected by the body interference filter and emitted from the one end surface of the focusing rod lens is incident again from the one end surface of the focusing rod lens; A third optical fiber guides the reflection spectrum component that enters the focusing lens again and is reflected again by the dielectric interference filter, and then enters the focusing rod lens from the first optical fiber and causes the dielectric interference. An optical demultiplexer comprising a light guide means for guiding transmitted spectrum components transmitted through the filter to a fourth optical fiber. (2. In the optical demultiplexer according to claim 1,
An optical demultiplexer comprising a light guiding means including a mirror that reflects a transmission spectrum component transmitted through a dielectric interference filter, the dielectric interference filter, and a focusing rod lens. (3) In the optical demultiplexer according to claim 1,
An optical demultiplexer in which a light guide means is constituted by a second focusing rod lens provided on the other end surface of a dielectric interference filter.