JP3339016B2 - Integrated transmission and reception optical communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication device, and more particularly, to an integrated transmission and reception optical communication device that performs transmission and reception using the same optical system.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a transmission / reception integrated optical communication apparatus to which the present invention is applied. The 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.

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 an S-polarized light reflection condition, 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 linearly polarized S-polarized light reflected by the polarization beam splitter 33 enters the light beam deflecting unit 20 via the λ / 4 plate 34. 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 light received 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.

[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.

At the time of installation and adjustment of this integrated transmission / reception type optical communication device, a paired opposing device is moved a predetermined distance, for example, 1 km.
It is essential to adjust the direction of installation while adjusting the direction of the remote location, while transmitting from one side and receiving on the other side. At the time of this adjustment work, it is desirable that the edge (peripheral edge) of the transmission light be clear to some extent while adjusting the diameter of the transmission light.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention, in particular, to provide a transmission / reception integrated optical communication device capable of clarifying the edge of transmission light.

[0008]

SUMMARY OF THE INVENTION A transmitting / receiving integrated optical communication apparatus according to the present invention includes a transmitting section including a semiconductor 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. A transmission / reception unit having polarization separation means for separating transmission light from the transmission unit and reception light to the reception unit; a telescope optical system common to a transmission / reception system for projecting transmission light and receiving reception light; and the telescope. Located between the optical system and the transceiver,
Light beam deflecting means driven according to the output of the position detecting element;
In the integrated transmission and reception optical communication device having a collimator lens that gives the emitted light beam from the semiconductor laser light source as a parallel light beam to the polarization separation means of the transmission and reception unit, near the surface of the collimator lens, the numerical aperture of the collimator lens, 80 to 90% of nominal minimum numerical aperture of semiconductor laser light source
It is characterized by a mask attached.

By providing such a mask, the peripheral edge portion of the laser beam emitted from the laser light source becomes clear (that is, the portion where the light beam exists and the portion where the light beam does not exist becomes clear), and the adjustment work is facilitated. Become.

[0010]

1 to 3 show a first embodiment 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. This embodiment does not sacrifice imaging performance,
In order to reduce the size of the deflecting optical system and the optical system following the deflecting optical system, the telescope optical system is divided into first and second afocal optical systems, and the intensity distribution of the transmitted light is made substantially circular with a circular cross section. The present invention is applied to an embodiment in which the beam diameter can be adjusted.

The telescope optical system 10 is composed of a first afocal optical system including a positive lens group 10A and a negative lens group 10B in order from the object side (light projection side). 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, emitted light is also substantially parallel. The diameter of the light beam is reduced toward the deflecting mirror 20. The diameter reduction ratio (magnification) can be, for example, about 1: 4 (four times).

A second afocal optical system 40 is provided between the deflecting mirror 20 and the transmitting / receiving section 30. The second afocal optical system 40 includes a positive lens group 40A and a negative lens group 4 in order from the deflection mirror 20 side to the transmission / reception section 30 side.
0B. This afocal optical system is also 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 light beam diameter is reduced from the 0 side to the transmitting / receiving section 30 side. The diameter reduction ratio (magnification) can be, for example, about 1: 2 (2 times). The positive lens group 40A and the negative lens group 40B of the second afocal optical system 40, on the other hand, the position of the negative lens group 40B is adjustable in the optical axis direction as shown by the arrow A in the illustrated example. When the position is adjusted, the beam diameter (divergence angle) emitted from the second afocal optical system 40, and hence the beam diameter (divergence angle) emitted from the telescope optical system 10, changes. When the beam diameter changes, the afocal property is slightly impaired, but the emitted light can be regarded as a substantially parallel beam. The means (mechanism) for moving and adjusting the negative lens group 40B includes:
Various lens moving mechanisms can be diverted. Also,
The magnification of the second afocal optical system 40 is set smaller than the magnification of the first afocal optical system, and by adjusting the luminous flux diameter (divergence angle) with the second afocal optical system on the side with the smaller magnification, Higher precision adjustment is possible. Also,
Since the movable weight is small, the mechanical structure is easy.

The light beam between the telescope optical system 10 and the second afocal optical system 40 is a substantially parallel light beam, and this parallel light beam enters the deflecting mirror 20. The deflection mirror 20 is
Driven in two orthogonal directions by a Y drive system 22,
When driven, this parallel light beam is deflected, and the light projecting direction of the transmission light or (and) the incident direction of the reception light to the transmission / reception unit 30 is adjusted. When the deflecting mirror 20 is arranged in the parallel light beam portion, there is an advantage that even if the light beam is deflected, the focus shift in the transmission / reception unit 30 does not occur.

A collimator lens 51 and an anamorphic optical system 50 as a beam shaping optical system are sequentially arranged between the semiconductor laser light source 32 and the polarizing beam splitter 33 in the transmitting / receiving section 30. The collimator lens 51 gives the laser beam from the semiconductor laser light source 32 as a parallel beam to the anamorphic optical system 50. The anamorphic optical system 50 includes a first prism 50A and a second prism 50B. This anamo optical system 50
Is for shaping a linear light beam emitted from the semiconductor laser light source 32 installed under the S-polarized light reflection condition into a circular light beam in a parallel light beam state. That is, as is well known, the light beam emitted from the semiconductor laser light source 32 composed of a laser diode has a linear or elliptical intensity distribution instead of a circular intensity distribution light beam. FIG. 2 is a schematic view thereof, in which the θ parallel direction (short axis direction) length θH is the θ vertical direction (long axis direction).
Shorter than the length θV. The anamorphic optical system 50 uses the first prism 50A and the second prism 50
By enlarging through B and making it substantially equal to the θ vertical length θV, the intensity distribution is shaped into a circle as shown by the broken line. Note that the θ parallel direction is the vibration direction of the linearly polarized light.

FIG. 3 shows a laser light source (laser diode).
32 shows a relationship between the collimator lens 32, a collimator lens 51, and a mask 58 attached to the collimator lens 51. The semiconductor laser light source 32 includes a light emitting unit 32a and a mask 32b. The semiconductor laser light source 32 is mounted on the mounting reference surface 3.
Variations in manufacturing are inevitable in the distance A from 2c to the light emitting portion 32a and the shift amount C in the direction orthogonal to the optical axis of the light emitting portion 32a, and the divergence angle (numerical aperture) changes like the angle B. . For this reason, the divergence angle is limited by the mask 32b, and the numerical aperture (NA) is kept constant. This numerical aperture is
Since the θ vertical direction and the θ parallel direction are different, the numerical aperture of the larger (θ vertical direction) is defined as the nominal minimum numerical aperture.

The collimator lens 51 itself has a sufficient numerical aperture to cover the maximum numerical aperture of the semiconductor laser light source 32. On the other hand, the mask 58 has the function of making the numerical aperture of the collimator lens 51 smaller than the nominal minimum numerical aperture of the semiconductor laser light source 32. That is, the effective range of the collimator lens 51 is narrowed. Specifically, the mask 58 sets the numerical aperture of the collimator lens 51 to about 80 to 90% of the numerical aperture of the semiconductor laser light source 32;
In other words, it is preferable to use one that cuts the periphery of the light beam emitted from the semiconductor laser light source 32 and limits the amount of emitted light to 80 to 90%. Explaining with specific numerical values, when the nominal minimum numerical aperture of the semiconductor laser light source 32 is, for example, 0.4, the mask 58 can use a collimator lens 51 with a numerical aperture of 0.34.

The position of the semiconductor laser light source 32 can be adjusted in the optical axis direction with respect to the collimator lens 51 as shown by an arrow B. By adjusting the position of the semiconductor laser light source 32 with respect to the collimator lens 51, the variation in the ratio of the length θV in the vertical direction and the length θH in the parallel direction of the semiconductor laser light source 32 can be adjusted to obtain a circular light beam.
In other words, while the magnification of the anamorphic optical system 50 is constant, the ratio (the ratio between the θ vertical length θV and the θ parallel direction length θH of the semiconductor laser light source 32 varies. This variation can be eliminated by adjusting the position of the semiconductor laser light source 32 in the direction of the optical axis during assembly to obtain a circular light beam. Means (mechanism) for adjusting the movement of the semiconductor laser light source 32
Can be diverted to various lens moving mechanisms.

It is known that the polarization beam splitter 33 has an angle dependence of transmittance (reflectance) depending on the angle of the incident light. Problem can be avoided. Therefore, the light is reflected by the polarization beam splitter 33 to reach the second afocal optical system 40, where
0, the transmission linearly polarized light beam of S-polarized light projected through the telescope optical system 10 is also a parallel light beam. The λ / 4 plate 34
Is for rotating the plane of polarization between the opposing devices by 90 °.

Focusing on the received light, the received light passing through the polarizing beam splitter 33 and the beam splitter 35 of the transmitting / receiving section 30 via the telescope optical system 10, the deflection mirror 20, and the second afocal optical system 40 is also a parallel light. Similarly, the problem of the angle dependence of the transmittance (reflectance) of the polarizing beam splitter 33 can be avoided. In a split optical path from the beam splitter 35 to the light receiving element 36, a condenser lens 52 and a band-pass filter 54 for forming an image of the received parallel light beam on the light receiving element 36 are arranged.
A condensing lens 53 and a band-pass filter 55 for forming an image of the received parallel light beam on the position detecting element 37 are arranged in the divided optical path from the light source to the position detecting element 37.

[0020] The integrated transmission / reception type optical communication apparatus having the above-described configuration includes:
At the time of installation, an apparatus 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 direction of the transmission light is adjusted. At this time, the laser beam emitted from the semiconductor laser light source 32 is emitted by the mask 58 through the collimator lens 51 whose numerical aperture is smaller than the numerical aperture of the semiconductor laser light source 32, and the circular beam is emitted by the anamorphic optical system 50. Becomes For this reason, the peripheral edge of the laser beam that is reflected by the polarization beam splitter 33, expanded in the beam diameter by the second afocal optical system 40, deflected by the beam deflector 20, and reaches the opposing device via the telescope optical system 10 is ,
It is clear and the adjustment work is easy.

In the use state, the opposing devices mutually receive the modulated signals from the modulator 31 with the light receiving element 36 for use. At this time, in the apparatus of the present embodiment, since the light beam from the semiconductor laser light source 32 is shaped into a circle by the anamorphic optical system 50 and the capture area is widened, reception by the telescope optical system 10 on the other side (opposite device) is not possible. It will be easier. Further, by adjusting the position of the negative lens group 40B of the second afocal optical system 40, the diameter of the light beam emitted from the telescope optical system 10 can be adjusted. Therefore, by adjusting the transmission beam diameter such that the diameter of the transmission light at the position of the telescope optical system 10 on the other side is slightly larger than the reception diameter of the telescope optical system 10 in accordance with the installation distance of the pair of devices. It is possible to always perform good optical communication. Also, since the afocal optical system is divided into first and second afocal systems located before and after the light beam deflecting means,
The size of the deflection optical system 20 and the polarization separation optical system 30 subsequent to the deflection optical system can be reduced without sacrificing the imaging performance.

In the above embodiment, the semiconductor laser light source 3
Although the anamorphic optical system 50 having a substantially circular cross-sectional shape of the light beam is inserted between the light beam 2 and the polarizing beam splitter 33, the present invention can be applied even when the anamorphic optical system is not inserted.

[0023]

According to the present invention, in the optical transmission / reception integrated optical communication device, the peripheral edge portion of the transmission light can be made clear and the workability at the time of installing the opposing device can be improved.

[Brief description of the drawings]

FIG. 1A is a system diagram showing a first embodiment of an integrated transmission / reception optical communication apparatus to which the present invention is applied. (B) (A)
FIG.

FIG. 2 is a schematic diagram showing a shape of a semiconductor laser light source in a cross section perpendicular to an optical axis and a state of beam shaping.

FIG. 3 is a sectional view showing a relationship between a mask of a collimator lens according to the present invention and a numerical aperture of a laser light source.

FIG. 4 is a system diagram showing an example of a conventional transmission / reception integrated optical communication device.

[Explanation of symbols]

 Reference Signs List 10 Telescope optical system (first afocal optical system) 20 20X 20Y Beam deflecting means (deflection mirror) 30 Transmitter / receiver unit 31 Modulator 32 Semiconductor laser light source 32a Light emitting unit 32b Mask 32c Mounting reference plane 33 Polarizing beam splitter 35 Beam splitter 36 Light receiving Element 37 Position detecting element 38 Signal processing circuit 40 Second afocal optical system 50 Anamo optical system (beam shaping optical system) 51 Collimator lens 58 Mask

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masakazu Yamagata 2-5-2 Higashi-Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. (72) Shun-ichiro Wakamiya 2-5-2 Higashi-Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. (56) References JP-A-6-125310 (JP, A) JP-A-4-351280 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10 / 00-10/28 H04J 14/00-14/08 G02B 13/00 G02B 17/08

Claims (1)

(57) [Claims] A transmitting unit including a semiconductor laser light source modulated in accordance with transmission information; a receiving unit including a light receiving element for receiving modulated laser light and a position detecting element; A transmission / reception unit having transmission light and polarization separation means for separating the reception light to the reception unit; a telephoto optical system common to a transmission / reception system for projecting transmission light and receiving the reception light; And a light beam deflecting means which is driven in accordance with the output of the position detecting element. The transmitting / receiving integrated optical communication device, wherein the light beam emitted from the semiconductor laser light source is converted into a parallel light beam and the polarization of the transmitting / receiving portion is changed. the collimator lens to provide the separating means is provided, in the vicinity of the surface of the collimator lens, said collimator lens
Is the nominal minimum numerical aperture of the semiconductor laser light source.
A transmission / reception integrated optical communication device, characterized in that the transmission / reception integrated optical communication device is provided with a mask that makes 80 to 90% of the above .