JP2000162465A - Cross talk preventing device for optical communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a cross talk between transmitted light and received light when a polarized light separating face and a light flux dividing face are arranged adjacently by providing a polarized light separating mirror and a light flux dividing mirror in a transmission/receiving part. SOLUTION: In a transmission/receiving part 30, a polarized light separating mirror 60 and a light flux dividing mirror 70 surrounded by air are arranged. In the polarized light separating mirror 60, a polarized light separating face PBS constructed of a polarized light separating film is formed on a transparent board. The light flux dividing mirror 70 is formed out of a light flux dividing surface BS on the transparent board by means of a light flux dividing film. Light flux from a laser light source 32 is incident on the polarized light separating mirror 60 and reflected by the polarized light separating face PBS, so that light flux of S polarized light rays alone is projected via a second focal optical system 40, a polarizing mirror 20, and a telescopic optical system. Light flux from the opposed machine passes through the polarized light separating mirror 60 so as to reach the light flux separating mirror 70. The light flux is divided via the light flux dividing face BS, and the divided light flux converges on a position detection element 37 and a light receiving element 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception integrated optical communication apparatus for performing transmission / reception using the same optical system, and more particularly to an apparatus for preventing crosstalk.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a transmission / reception integrated optical communication apparatus to which the present invention is applied. This optical communication device includes a telescope optical system 10, a light beam deflecting unit 20,
And a transmission / reception unit 30. The telescope optical system 10
It is commonly used for projecting transmission light and receiving reception light, and in the example shown in the drawing, comprises a reflection telescope. The light beam deflecting unit 20 is located between the telescope optical system 10 and the transmission / reception unit 30, and determines the direction of the reception light from the telescope optical system 10 to the transmission / reception unit 30 and the direction of the transmission light from the transmission / reception unit 30 to the telescope optical system 10. Adjust.

[0003] A transmitting / receiving section 30 is provided with a semiconductor laser light source 32 which is modulated in accordance with transmission information by a modulator 31 and is provided under S-polarized light reflection conditions, and an S-polarized light beam from which a linearly polarized light beam from the semiconductor laser light source 32 is incident. And a polarization beam splitter 33 that transmits the reflected P polarized light. The transmitting and receiving unit 30 includes:
In order to receive the signal light from another optical transmitter (opposite device), a beam splitter 35 is provided on the transmission optical path of the polarization beam splitter 33, and this beam splitter 35 is provided.
The light receiving element 36 for signal and the position detecting element 37 are provided on the divided optical path in the above. That is, the received light from the opposing device is transmitted through the λ / 4 plate 34 to be linearly polarized light of P polarization, transmitted through the polarization beam splitter 33 and reaches the beam splitter 35, and is transmitted to both the light receiving element 36 and the position detecting element 37. Incident on. The received light received by the light receiving element 36 is extracted as information by the signal processing circuit 38. Polarizing beam splitter 33 and beam splitter 3
5 has a polarization splitting surface and a light beam splitting surface formed on a bonding surface of a pair of prisms.

[0004] The above-mentioned transmission / reception integrated optical communication apparatus is usually
A device having the same configuration is installed so as to face the reach of the laser beam from the semiconductor laser light source 32, and the modulators 31
Is used by receiving the modulated signal by the light receiving element 36.

[0005] The light beam deflecting means 20 is for maintaining the parallelism of the transmitted and received light from the pair of optical communication devices.
It comprises a deflecting mirror driven in two orthogonal directions. The rotating portion of the deflecting mirror is provided with an electromagnetic driving device including a coil and a magnet, and the electromagnetic driving device is driven by the output of the position detecting element 37. That is, the position detection element 37 detects the reception position (change) of the reception light input to the transmission / reception unit 30 and feeds back its output via the control circuit 21 and the XY drive system 22 to move the deflecting mirror 20 to the XY position. The transmission / reception unit 30 is driven in the three-dimensional
To maintain the parallelism between the emitted light of the transmitter and the received light of the receiver.

[0006] In the conceptual configuration of FIG. 3, the transmission / reception integrated optical communication device includes a transmission light from a semiconductor laser light source 32,
There is no risk of crosstalk between the signal light receiving element 36 and the received light to the position detecting element 37. However, in the actual device configuration, the polarization separation by the polarization beam splitter 33 is not 100% complete (a complete polarization separation film configuration is practically impossible, and leakage light (stray light) of several% cannot be avoided. ), Reflection on the input / output surface of the polarizing beam splitter 33 and the beam splitter 35 is unavoidable, and there is a high possibility that the polarizing beam splitter 33 and the beam splitter 35 are installed close to each other. There is a possibility that crosstalk in which the transmitted light is incident on the light receiving element or the position detecting element on the receiving side may occur.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a transmission / reception integrated optical communication device which can solve the problem of crosstalk between transmitted light and received light when the polarization splitting surface and the light beam splitting surface are installed adjacent to each other. Aim.

[0008]

SUMMARY OF THE INVENTION In the present invention, the problem of reflection of a light beam on the input / output surface is solved by using a polarizing beam splitter in which a pair of prisms are bonded as a polarization splitting surface and a beam splitter in which a pair of prisms are bonded as a light beam splitting surface. This is because it is possible to avoid the problem of reflection such as the case where light enters and exits the prism if the surroundings are constituted by a polarization splitting mirror and a beam splitting mirror of air. .

That is, the present invention provides a transmitting section including a laser light source modulated in accordance with transmission information, a receiving section including a light receiving element for receiving modulated laser light and a position detecting element, and a transmitting light from the transmitting section. A transmission / reception unit having polarization separation means for separating the reception light to the reception unit; a telephoto optical system common to the transmission / reception system for projecting the transmission light and receiving the reception light; and between the telephoto optical system and the transmission / reception unit. A transmitting / receiving integrated optical communication device having a light beam deflecting means positioned and driven in accordance with the output of the position detecting element, wherein the transmitting / receiving unit reflects the transmission light from the laser light source toward the light beam deflecting means while using a telescope. A polarization splitting mirror having a polarization splitting surface that transmits received light incident thereon, and a light beam splitting mirror having a light beam splitting surface that splits the received light transmitted through the polarization splitting surface into the light receiving element and the position detecting element. It is characterized by providing.

[0010]

FIG. 1 shows a first embodiment of a transmission / reception section of a transmission / reception integrated optical communication apparatus according to the present invention. The same components as those of the conventional apparatus of FIG. It is attached. In the present embodiment, a second afocal optical system 40 is arranged between the deflecting mirror 20 and the transmission / reception unit 30. The second afocal optical system 40 includes the positive lens group 4 in order from the deflection mirror 20 side to the transmission / reception section 30 side.
0A and a negative lens group 40B. An afocal optical system is an optical system in which a set of object points and an image point are at infinity, and when incident light is substantially parallel, outgoing light is also substantially parallel,
The beam diameter is reduced from the object side to the 30 side. This diameter reduction ratio (magnification) is determined by the telescope optical system (first afocal optical system) 10
Of the second afocal optical system 40 can be made 1: 2 (about 2 times).

In the transmitting / receiving section 30, a polarization splitting mirror 60 and a light beam splitting mirror 70 whose surroundings are air (space) are located. These replace the prism-bonded beam splitter 35 in the same manner as the prism-bonded polarization beam splitter 33 in the conventional apparatus shown in FIG. The polarization separation mirror 60 is formed by forming a polarization separation surface PBS on a transparent substrate (parallel plane plate) using a polarization separation film. The polarization separation surface PBS is connected to the optical axis 32X of the semiconductor laser light source 32 and the second afocal point. 4 on the optical axis 40X of the optical system 40
They are arranged at 5 mm. The light beam splitting mirror 70
Similarly, a light beam splitting surface BS is formed on a transparent substrate (parallel flat plate) by a light beam splitting film.
Are the optical axis 40X of the second afocal optical system 40 (the optical axis 36X of the light receiving element 36) and the optical axis 3 of the position detecting element 37 system.
Each of them is arranged at an angle of 45 ° with respect to 7X.

On the optical axis 32X of the semiconductor laser light source 32, there is provided a collimator lens 51 for converting a light beam from the semiconductor laser light source 32 into a parallel light beam. A condensing lens 52 for forming an image on the light receiving element 36 and a band-pass filter 54 are arranged. On the optical axis 37X of the position detecting element 37, a condensing lens 53 and a band for forming an image of the received parallel light beam on the position detecting element 37 are provided. A pass filter 55 is provided. Light receiving element 36
And the position of the position detecting element 37 can be exchanged.

Semiconductor laser light source 32 and polarization split mirror 6
The 0 polarization separation plane PBS is installed under the S polarization reflection condition. After being emitted from the semiconductor laser light source 32 and converted into a parallel light beam by the collimator lens 51, the polarization splitting mirror 60
The S-polarized light beam reflected by the polarization separation surface PBS is projected to the optical communication device on the other side through the second afocal optical system 40, the deflecting mirror 20, and the telescope optical system 10. Focusing on the received light, the received light transmitted through the P-beam splitting surface BS of the polarization separation mirror 60 of the transmission / reception unit 30 via the telephoto optical system 10, the light beam deflecting means 20, and the second afocal optical system 40 is a parallel light beam. Therefore, the problem of the angle dependence of the polarization separation surface PBS can be avoided. The λ / 4 plate 34 is for rotating the polarization plane between the opposing devices by 90 °.

The transmission / reception integrated optical communication device having the above-described configuration is:
Similar to the conventional device, a device having the same configuration is installed facing the reach of the laser beam from the semiconductor laser light source 32,
The modulated signals from the modulator 31 are mutually received by the light receiving element 36 and used. At this time, the laser beam from the semiconductor laser light source 32 enters the polarization separation mirror 60 and is reflected by the polarization separation surface PBS, and only the S-polarized light beam passes through the second afocal optical system 40, the deflection mirror 20, and the telescope optical system 10. It is projected through. The light beam from the opposing device is transmitted to the telescope optical system 10, the second afocal optical system 40, and the deflecting mirror 20.
Through the polarization separation mirror 60, and the polarization separation surface PBS
And reaches the light beam splitting mirror 70. In the light beam splitting mirror 70, the light beam is split via the light beam splitting surface BS, and the split light beam is split into the position detecting element 37 and the light receiving element 36.
Will be collected.

The polarization splitting by the polarization splitting mirror 60 and the light splitting by the light splitting mirror 70 are performed by an air (space) mirror in the surroundings. No problem. That is, a signal having a high SN ratio can be obtained.

The polarization splitting mirror 60 and the light beam splitting mirror 70 may be formed in a wedge shape as shown in FIG. 2 in order to reduce the influence of the back surface reflection.

[0017]

According to the present invention, the problem of crosstalk can be avoided in an optical communication device integrated with transmission and reception.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a transmission / reception unit of a transmission / reception integrated optical communication device according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the transmission / reception unit of the integrated transmission / reception optical communication device of the present invention.

FIG. 3 is a system diagram showing an example of a conventional transmission / reception integrated optical communication device.

[Explanation of symbols]

 Reference Signs List 10 telephoto optical system (first afocal optical system) 20 light beam deflecting means 30 transmitting / receiving unit 31 modulator 32 semiconductor laser light source 36 light receiving element 37 position detecting element 38 signal processing circuit 40 second afocal optical system 60 polarization separating mirror 70 light beam Split mirror PBS Polarization splitting surface BS Beam splitting surface

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuo Goto 2-5-2 Higashi-Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. (72) Inventor Yume Takayama 2-5-Higashi-Oizumi, Nerima-ku, Tokyo No. 2 Asahi Seimitsu Co., Ltd. (72) Inventor Yoichi Kojima 2-5-2 Higashi Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. F-term (reference) 2H087 KA22 LA21 LA25 LA26 PA01 PA02 PA17 PB01 PB02 QA02 QA06 QA14 QA22 QA39 QA41 5K002 AA05 AA07 BA02 BA13 BA21 CA21 FA04 9A001 BB04

Claims (1)

[Claims] A transmitting section including a laser light source modulated in accordance with transmission information; a receiving section including a light receiving element for receiving modulated laser light; and a position detecting element; transmitting light from the transmitting section; and the receiving section. A transmission / reception unit having polarization separation means for separating the reception light into the transmission / reception unit; a telephoto optical system common to the transmission / reception system for projecting the transmission light and receiving the reception light; and being located between the telephoto optical system and the transmission / reception unit. An optical communication device comprising: a light beam deflecting device driven in accordance with an output of the position detecting element; wherein the transmitting / receiving unit reflects transmission light from the laser light source toward the light beam deflecting device, and receives light from a telescope. And a light beam splitting mirror having a light beam splitting surface for splitting the received light beam transmitted through the polarized light splitting surface into the light receiving element and the position detecting element. This Crosstalk preventing device of an optical communication apparatus according to claim.