JPS59204025A - Optical branching and coupling device - Google Patents

Abstract

PURPOSE:To obtain an optical accessor by which a crosstalk to an optical signal brnach terminal from an optical signal inserting terminal is small, and also a passing loss of a light of a main line is low, by leading an abnormal light of a parallel incident light from the first light incident end to the second light emitting end separated from the first emitting end by making a normal light from the second light incident end coincide with an optical axis. CONSTITUTION:A light which is made incident to the end face of calcite 14 from an incident terminal 1 to an optical accessor is separated into an abnormal light and a normal light, and this normal light is led to an optical signal branch terminal 3. Also, the abnormal light is led to an emitting terminal 2 by making the normal light from an optical signal inserting terminal 4 coincide with an optical axis in a photodetecting side end face 15 of the calcite 14, and goes into an optical fiber of a main line. In this case, said lights must be separated completely in the photodetecting side end face 15 of the calcite 14 so that the normal light from the optical signal incident terminal 4 does not cause a crosstalk to the optical signal branch terminal 3. Also, in order to prevent a fact that the abnormal light from the optical signal inserting terminal 4 is reflected by the side face of a calcite plate 14, and causes a crosstalk to the optical signal branch terminal 3, an absorbing plate 16 is stuck to the side face of the calcite plate 14. According to such a constitution, a passing loss to the emitting terminal 2 from the incident terminal 1 becomes low, a crosstalk to the optical signal branch terminal from the optical signal inserting terminal 4 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention branches a main optical signal connecting stations at a station of an optical transmission system in which the source is a signal transmission medium. Alternatively, it relates to an optical branching/coupling device (formerly known as an accessor) having the function of inserting an optical signal into a trunk line.

Conventional configuration and its problems All functions of the original accessor will be explained with reference to FIG.

The source accessor in FIG. 1 is arranged as a VC between the source fiber main lines of an optical transmission system in which all transmission lines are made of one fiber.

1 is the terminal for inputting the element 11 from the original fiber of the trunk line to the optical accessor, and 2 is the terminal for inputting the element 12 from the original accessor to the original fiber of the trunk line.
3 is a terminal for branching and outputting the optical signal from the main line, and 4 is a terminal for inserting the optical signal β4 into the main line. Each terminal 1 to 4 is composed of an original fiber 5 serving as a transmission path and a collimator lens 6. Here, the collimator lens 6 is used to convert the light emitted from the single fiber 5 into parallel light beams (or to condense the parallel light beams into the optical fiber 5).

The conventional original akudesu will be explained in Figures 2 and 3.

Figure 2 shows that a no-f mirror is used for light-sound splitting.
Optical elements 7 and 8, such as ND filters, which have a function of reflecting part of i are used. Of the light emitted from the light input terminal 1 to the original accessor.

The light transmitted through the optical elements 7 and 8 exits from the light output terminal 2. The input signal input from the original signal insertion terminal 4 is optical, (...
It is reflected by −8, and the original and the original from terminal 1 are 11i1+1
However, in this method, out of the light incident from terminal 4, the collimator lens end 9 of terminal 2 or The source 71!5 reflected by the optical fiber mating end face of the source fiber connector (not shown) re-enters the source accessor, and further enters the source fiber existing at the colinator lens end 10 of the terminal 1 or beyond it. It is reflected from the mating end face of the original fiber of the fiber optics (not shown), enters the three-dimensional optical element 7, is reflected by the optical element 7, crosstalks to the terminal 3, and causes S/N deterioration] In order to reduce the amount of crosstalk, the original fiber mating end face of the single fiber connector is set at an angle (I
Difficult measures such as holding the surface on the JI @ side are required.

In this method, the source guided from terminal 1 to terminal 2 passes through two optical elements 7 and 8 on the way.

Since a portion of the signal is reflected and lost at each point, the transmission loss from terminal 1 to terminal 2 is essentially as large as 6 dB or more, which limits the transmission distance.

FIG. 3 shows another conventional example. 11 is a beam splitter
, Glan-Thompson, etc., the light incident on the light input terminal 1 to the source accessor is polarized and separated into two mutually orthogonal directions. Of the two polarized lights, one polarized light enters the output terminal 2 and is guided to the main fiber. The other one of the two polarized lights is guided to the optical signal branching terminal 3. Then, the source input from the optical signal insertion terminal 4 is deflected by the polarizing prism 12, reflected by the surface 13 of the polarization splitting prism 11 having a polarization splitting function, and then transmitted from the output terminal 2 to the main optical fiber. be guided.

In this method, the degree of polarization separation of the polarization separation prism 11 and the degree of polarization of the polarization prism 12 are -1.

Crosstalk 'U1 from optical signal insertion terminal 4 to original signal branch terminal 3
; t/(m), and it is difficult to reduce the dR speech loss.

1. An object of the present invention is to provide an optical accessor with fewer transmissions from the original signal insertion terminal to the original signal branch terminal, and with a lower transmission loss of main line light. do.

Structure of the Invention The present invention is based on one end 1'f of a uniaxial crystal whose surface is cut in the direction in which the angle of separation 11 between ordinary light and extraordinary light is approximately maximum.
ll V'C, the first and second light incident ends are connected to the end face Vc of the crystal body. A second light emitting end is arranged, and ordinary light that is parallel incident from the first light incoming end to the -axial crystal body is equalized to the first light emitting end, and the yL light of the first light emitting end is The extraordinary light of the parallel incident light from the input ends is made to coincide with the lightning from the light input ends of A1 and 2 above and the original Qll.

1) The second light emitting end is located at a position separate from the emitting end of test writing 1.

DESCRIPTION OF THE EMBODIMENTS FIG. 4 describes the configuration of a source accessor according to an embodiment of the present invention. Reference numeral 14 denotes a uniaxial crystal plate whose surface is cut out in the direction in which the angle of separation between the ordinary light and the extraordinary light is maximum. Reference numeral 1 denotes a terminal through which light from the original fiber of the trunk line enters the optical accessor.

A parallel round line that is incident from the input terminal 1 onto one of the -M planes of the -axial crystal flat plate 14 is separated into ordinary light and extraordinary light. To Hyeon-chung: Lead to branch terminal 3. When the abnormality M occurs, the optical axis of the original light incident on the uniaxial crystal plate 14 from the original signal insertion terminal 4 coincides with that of the original light, and the light is transmitted to the output terminal 2 and enters the main fiber. At this time, in order to prevent the ordinary light from the original signal input terminal 4 from crosstalking to the original signal branch terminal 3, the lightning from the terminal 4 and the ordinary light from the input terminal 1 are arranged at the light receiving side end face 15 of the uniaxial crystal flat plate 14.

Configure to be fully isolated. Note: 1 Uniaxial crystal flat plate 1401111 of extraordinary light from optical signal insertion terminal 4
In order to prevent the reflected component on one surface from crosstalking to the signal branch terminal 3, an absorption plate 16 is installed on the side surface of the -axial crystal flat plate 14.

The crosstalk loss from the ffS signal insertion terminal 4 to the original signal branch terminal 3 according to the present invention is as follows. The ordinary light from the original signal insertion terminal 4 is partially reflected by the collimator lens end face 9 of the output terminal 2 or the tongue of the redundant fiber mating end face (not shown) of the original fiber connector located beyond that, and then -
The light is incident on the axial crystal flat plate 14. Since this source is C which is biased in the same direction as the ordinary light, it follows the same optical path as the ordinary light and reaches the original signal! ↑1 person ψ:lii = r-4K return. Furthermore, the two light components in the polarization direction perpendicular to the ordinary light that re-entered the −-axis crystal flat plate 14 are guided to the input terminal 1 along a circular optical path with the extraordinary light from the input terminal 1 . Therefore, if there is crosstalk from terminal 4 to terminal 3, the crosstalk loss from terminal 4 to terminal 3 will be 50 dB. It's ox, -II! Part III When the light from terminal 1 enters the crystal plate 14, it is separated into two components: ordinary light and extraordinary light.

Since the extraordinary light component is directly guided to the output terminal 2, a passing Jj-i loss of 3 dB from the input terminal 1 to the output terminal 2 in the present invention can be achieved.

By the way, the light from the light input terminal 1 guided to the light output terminal 2 and the original signal from the original signal insertion terminal 4 are as follows.

It is a source of light that is polarized in one direction. When this polarized light is incident on the original accessor of the next stage, the branching ratio at which the polarized light is branched from the input terminal 1 to the original output terminal 2 and the original signal branch terminal 3 changes. In order to avoid this, it is recommended to make the polarized J light into circularly polarized light through one plate (λ: original signal wavelength), which is led to the terminal λ 2, and then input it to the primary accessor of the first stage. It's heavy.

Next, an embodiment of the present invention will be described in detail.

The original fiber of the main transmission line of the optical transmission system to which this embodiment is applied has, for example, a core diameter of 50 μm.

A Q, 85 μm laser diode is used as a light source. A self-focusing lens is used as the collimator lens so that the light emitted from the 1-element fiber becomes parallel light at the end face of the 131 self-focusing lens.

Dimensions. - Determine the pitch length of the self-focusing lens so that the light transmitted through the axial crystal flat plate can be focused into the original fiber. As the axial crystal flat plate 14, calcite was used here.

When the direction is determined and the plane is cut out so that the original axis of the calcite is at an angle of about 42 degrees with respect to the plane of incidence, the separation angle between the ordinary light and the extraordinary light is at its maximum.

Its separation angle is 6.252.

The light that enters the end face of the calcite 14 from the input terminal 1 to the optical accessor is separated into extraordinary light and ordinary light, and this ordinary light /(, () is guided to the No. 11 branch terminal 3.
L, X: ordinary light from fi bow insertion terminal 4 and calcite 14
Align the light 1 with the light-receiving side end face 15 of the
It is guided by F2 and enters the main fiber. This “T”
, L 'l:j':>-original signal branch from input terminal 4 j:! ;"I" 3 hair) 1 soba Ji L I V
+ Mr. Ni 1 both receive Calcite 14! :111':
! 1i il 15 must be completely separated (t, 1.4 cm). The beam diameter of the parallel 1. ray that is transmitted through the calcite plate 14 is approximately O97mTn.
The old model (the beam diameter can also be widened is also a part of the problem).
The light-receiving side end surface 15 of the stone flat plate 14 is used to connect the ordinary light from the input terminal 1 and the . : To separate it, it is sufficient to have 1 car) ℃ line's original 1 孝 or 10111711 separation nine. In order to obtain a separation distance of 10 points between ordinary light and abnormal light at the light receiving end 1 and 15 of the calcite flat plate 14, the calcite flat plate 14 must be
The thickness of 9.5 votes or more is required.

The abnormal light from the optical signal insertion terminal 4 is the calcite plate 14.
An absorbing plate 16 is attached to the side surface of the calcite flat plate 14 to prevent it from being reflected at the side surface and crosstalking to the optical signal branching terminal 3.
I can ask.

When the optical accessor of the present invention was prototyped with the above design, the passage loss from the input terminal 1 to the output terminal 2 was 6 dB or less.
The branching loss from input terminal 1 to 1 optical signal branching terminal 3 is 5d.
Below B, optical signal insertion Q: h: Coupling loss from child 4 to output terminal 2 is sdB or more F, optical I? The loss from the No. J insertion terminal 4 to the optical signal branching terminal 3 was 50 dB or more.

Note that, in addition to the calcite used in this embodiment as the Qqlt crystal flat plate 14, the same effect can be obtained by using rutile, wurtzite, or the like.

1. In this example, we used all the terminals consisting of the 1.degree. combination of the optical fiber and the collimator lens, including the input end of 1 element and the output end of "1". There is no problem if it can be input.In addition, the single signal input terminal 4
, the incident ray becomes a parallel ray, and the direct 2
The same effect can be obtained even if the generator element is attached to the end face of the uniaxial crystal flat plate 14.

Here, if a polarized principal input source such as a laser beam is used, the crosstalk loss can be further increased. In addition.

As the original signal branch terminal 3, glue the -axial crystal flat plate 14.
However, even if a light receiving element is directly attached, the same effect can be obtained.

Next, as mentioned above, the original accessor 10 according to the present invention
An example in which a λ/4 plate 300 is inserted between 0.0 and 200 mm is shown in FIG. 5. In FIG.
'yt,i from 04 are linearly polarized lights with mutually orthogonal polarization directions. When the transmission distance between the original accessor 100 and the next-stage original accessor 200 is short, the deflection direction of the original input from the input end 201 is not completely random;
Depending on the polarization state, the main optical signal is sent to the optical signal branch terminal 20.
3 and the output terminal 202 change. In order to prevent this, the original accessor 100 and the next stage original accessor 20
The λ/4 plate 300'i may be placed between 0 and 0, so that the linearly polarized light becomes circularly polarized light and enters the original accessor of the next stage.

Effects of the Invention According to the present invention, it is possible to obtain a source accessor that has very high crosstalk loss from the source signal insertion terminal to the optical signal branch terminal and has low original transmission loss of the main line.

The present invention greatly contributes to the realization of high-performance optical transmission equipment that performs optical signal dropout and addition.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the functions of the optical accessor.
FIG. 2 is a schematic diagram of a conventional source accessor using an optical element having the function of reflecting a portion of the source. FIG. 3 is a schematic diagram of a conventional source accessor using a polarization separation element, and FIG. 4 is a configuration diagram of a source accessor according to an embodiment of the present invention.
FIG. 5 is a diagram showing an example of a combined state of original accessors according to the present invention. 1... Terminal that inputs the source from the source fiber of the main line to the source accessor, 2... Terminal that outputs the source from the source accessor to the nine fibers of the main line, 3...... Main line Terminal for branching the original signal from 4... Eggplant for inserting the optical signal into the main line, 5... Original fiber, 6...
...collimator lens, 14...-axial crystal flat plate, 15...--light receiving side end surface of axial crystal flat plate, 1
6...Absorption plate. Name of agent: Patent attorney Makoto Nakao and 1 other person 1st
Figure @ 2 @ Figure 3 ↑ Figure 5

Claims (2)

[Claims] (1) Attach the first and second light incident ends to one end face of a uniaxial crystal cut out from i (6f) in the direction where the separation angle between lightning and extraordinary light is almost maximum. 1st.
A second light emitting end is disposed, and a parallel incident light beam (')) YOZ from the first light incident end to the pre-occupying-axis crystal body is guided to the first light emitting end. 1) The extraordinary light of the parallel incident light from the light input end of 1' trial writing 1 is made to have its original axis coincident with the ordinary light from the second light input end, and is separated from the first output end. A light branching/coupling device characterized in that the light is guided to the light emitting end of the whistle 2 before the light is located at a defined position. (2) The polarized light guided to the second light output yiii1i+ is λ/
An anti-coupling device for dividing a circle (iji element t/(m) according to claim 1) using four plates.