JP2743661B2 - Light beam tracking reception method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam tracking receiving system for tracking a received light beam in a space propagation type optical communication receiver.

[0002]

2. Description of the Related Art In this type of conventional light beam tracking reception system, a four-division light receiving element is placed at the focal point of a light receiving lens system, and the direction of arrival of the received light depends on which quadrant has a spot of the received light. The shift of the optical axis of the receiving lens system is detected, and the tracking operation is performed so as to minimize the shift.

A conventional example will be described with reference to the drawings.
The schematic side view of (a) shows the lens 41 and the four-divided light receiving element 4
2 shows an optical beam tracking receiving method including the second method, and FIG.
Shows a schematic front view of the four-division light-receiving element 42. In this light beam tracking reception system, the light-receiving elements 42a to 42d arranged in four quadrants of the four-division light-receiving element 42 at the focal position of the lens 41, respectively. From each of the electrodes 43 to
46 is drawn out, the current flowing between any one of the electrodes 43 to 46 and the common ground electrode 47 is detected, and the direction of the incoming received light A is known. That is, it is known that the spot of the received light A exists in the light receiving element (any one of 42a to 42d) where the current is generated, and it can be detected that the direction of the received light A is shifted in a symmetric direction with respect to the optical axis 48. . For actual light beam tracking, four light receiving elements 42a to 42d
It is not enough to simply provide information on which light receiving surface the spot is on, and in many cases it is necessary to provide information on in which direction the spot is displaced. There is a case where the spot of the received light A is widened by slightly shifting the position on the axis 48, and the received light A simultaneously straddles a plurality of the light receiving elements 42a to 42d as shown by the hatched portion in FIG.

In this case, the amount of light received by each of the light receiving elements 42a to 42d changes in accordance with the amount of deviation of the center of the spot of the received light A from the center of the four-divided light receiving element 42. , 46 also change, and thereby the direction and extent of the shift of the received light A can be determined.

[0005]

In this conventional light beam tracking receiving system, a four-division light receiving element is used as a light receiving element for communication, which is lower in sensitivity and response speed than the dedicated communication light receiving element. Use a separate light-receiving lens system separate from the communication system, or use a single light-receiving lens system optically coupled to the optical axis of the communication system. There was a problem in terms of losses.

[0006]

According to the present invention, there is provided a light beam tracking receiving system, comprising: a light beam tracking receiving system for detecting an angular deviation of incident received light to generate a tracking signal; A light receiving means in which the diameter of the spot is substantially equal to the diameter of the circular light receiving surface of the light receiving element receiving the condensed spot, and the condensed spot is disposed on a circumference substantially equidistant from the center of the light receiving surface of the light receiving element. the collection is rotated in a circular
Light spot rotation driving means, and a condensing spot for controlling the center of rotation to move to the center of the light receiving surface of the light receiving element
Rotation center control means .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

[0008] Figure 1 shows a light beam tracking receiver device included in the optical communication receiver according to an embodiment of the present invention, FIG. 1 (a) is a block diagram of an embodiment, FIG. 1 (b) and
(C) is a diagram showing a positional relationship between a light receiving surface of a light receiving element used in the present embodiment and a received light spot.

The light receiving lens system including the mirrors 1, 2, and the lens 3 and the optical receiver 4 in the embodiment of FIG. 1A also serve as the communication system. Mirror 1 for receiving incoming light A
Is controlled by a control voltage V1 output from an X-direction control output terminal 35 of the drive circuit 6, and rotates around an axis perpendicular to the paper by an angle proportional to the control voltage V1. Mirror 1
The mirror 2 that emits the received light A received from the lens 3 to the lens 3
It is controlled by a control voltage V2 output from a Y-direction control output terminal 36 of the drive circuit 6, and rotates around an axis at which the paper surface and the mirror 2 intersect in proportion to the control voltage V2. Optical receiver 4
Receives the condensed spot B of the received light A from the lens 3, outputs a communication signal from a signal output terminal 5 to a communication device (not shown), and displays an AGC representing a reception level of the received light A from another terminal. It outputs a reception level signal Vs such as a voltage.

Here, the control voltage V1 is V1 = X + a ·
sinωt (X is bias, a is constant, ω is angular frequency,
t is a signal represented by (time). The bias X is a control signal x input from the attitude control device (not shown) of the optical communication receiver to the X direction control input terminal 33 and a reception level signal input from the optical receiver 4 to the reception level input terminal 21. Vs and the angular frequency ω is set to a value that gives the mirrors 1 and 2 an appropriate rotation speed by the drive circuit 6 itself. Similarly, the control voltage V2 is V2 = Y + a · co
This is a signal represented by sωt. The bias Y is also generated based on the control signal y input from the attitude control device to the Y-direction control input terminal 34 and the reception level signal Vs.

Therefore, the light flux of the received light A incident on the lens 3 draws a circle around a point determined by the biases X and Y in time by two-dimensional control by the control voltages V1 and V2. As a result, the center of the (convergent) spot B of the received light A connected to the light receiving element (light receiving surface 11) of the optical receiver 4 that receives the received light A from the lens 3 also draws a circle.

The amount of change in the magnitude of the control voltages V1 and V2 according to the angular displacement ωt is determined by a constant a. Therefore, as shown in FIG. 1B, the focus of the light receiving lens system is slightly shifted, and the diameter of the circle drawn by the center of the spot B of the received light A is substantially equal to the diameter of the light receiving surface 11 of the light receiving element of the same shape. A constant a is determined so as to have the same size.

Further, the drive circuit 6 has a function of the angular displacement ωt of 0 to 2
By changing the amount of received light (the level of the received light A input to the light receiving element of the optical receiver 4) up to π, the values of the biases X and Y are controlled as described later with reference to FIG. Is controlled so as to minimize the level change of the reception level signal Vs in one cycle. That is, the driving circuit 6,
The light receiving lens system, the optical receiver 4 and the attitude control device constitute a negative feedback circuit for inputting the received light A to the light receiving surface 11 with the maximum level and a small change in the received level.

Therefore, the optical beam tracking receiver of FIG.
With respect to the incident angle deviation of the received light A within the range limited by the variable range of the mirrors 1 and 2, the spot B always connected to the light receiving surface 11 has a constant circumference from the center of the light receiving surface 11 as shown in FIG. Stable at the point of rotation above. Since the biases X and Y correspond to the amount of change in the optical axis of the light receiving lens system, the biases X and Y are taken out to the X-direction angle signal output terminal 7 and the Y-direction angle signal output terminal 8, respectively, and are used for optical communication reception. The attitude control of the entire machine is performed, and the control signals x,
Obviously, it is possible to obtain y and guide the biases X and Y to the points where X = 0 and Y = 0, respectively.

Next, the driving circuit 6 will be described in detail with reference to FIG.

The receiving level signal Vs applied from the optical receiver 4 shown in FIG. 1 to the receiving level input terminal 21 and the sine wave signal sinωt output from the oscillator 24 are multiplied by a multiplier 22.
To produce the signal Vs · cosωt.
If the time change of Vs and cosωt are in phase, the signal V
s · cos ωt has a large amplitude, and if the phases are opposite, they cancel each other and become small. The signal Vs · cosωt is averaged by one cycle (0 to 2π) of the angular displacement ωt by the low-pass filter 25.
1 is taken out, and a control signal x, which is a component for correcting the X-direction optical axis shift peculiar to the optical receiver 4 input from the X-direction control input terminal 33, is added by an adder 27 to generate a bias voltage (FIG. In the description of 2, the bias is referred to as a bias voltage) X. The bias voltage X is output to the X-direction angle signal output terminal 7 and the oscillator 24
The output obtained by multiplying the sine wave signal sinωt from the output signal by a by the amplifier 29 and the adder 31 are added to obtain a control signal V1 = X + a · sinωt as a result of the addition. The control signal V1 is output to the X-direction mirror control terminal 35.

Similarly, the sine wave signal sinωt output from the oscillator 24 becomes a signal cosωt via the 90 ° phase shifter 33, and this signal is multiplied by the reception level signal Vs by the multiplier 23 to obtain the signal Vs・ Sinωt
Is obtained. The signal Vs · sin ωt is output from the low-pass filter 26.
The average value Y1 of one cycle of the angular displacement ωt is extracted by
This and a control signal y which is input from the Y-direction control input terminal 34 and is a component for correcting the Y-direction optical axis deviation peculiar to the optical receiver 4 are added by the adder 28 to generate a bias voltage Y. The bias voltage Y is applied to the Y-direction angle signal output terminal 8
And the signal c from the 90 ° phase shifter 33
The output obtained by multiplying osωt by a by the amplifier 30 and the adder 3
2 and a control signal V2 = Y + a resulting from the addition
・ Cosωt is obtained. The control signal V2 is output to the Y-direction mirror control terminal 36.

As described above, the bias voltages X and Y become voltages having large absolute values when the direction of the spot of the received light A oscillated by the mirrors 1 and 2 coincides with the displacement direction of the spot B actually received. Can be used as angle information for controlling the attitude of the optical receiver.

[0019]

As described above, according to the present invention, the condensed spot of the received light rotates around a single light receiving element, and the condensed spot is located on the circumference equidistant from the center of the light receiving element. Is controlled so as to rotate, and from the reception level of the reception light and the change in the reception level, the deviation of the angle between the optical axis and the reception light and the magnitude thereof can be detected, and the reception optical system is used for the communication system and the tracking system. Since there is no need for an element that causes optical loss on the optical path, it is advantageous in that the optical system can be reduced in size and weight while compensating for the loss due to the spot of the received light overflowing from the light receiving element.

[Brief description of the drawings]

FIG. 1 shows an optical beam tracking receiver included in an optical communication receiver according to an embodiment of the present invention. FIG. 1 (a) is a block diagram of the embodiment, and FIGS. 1 (b) and (c). FIG. 3 is a diagram showing a positional relationship between a light receiving surface of a light receiving element used in the embodiment and a received light spot.

FIG. 2 is a configuration diagram of a drive circuit 6 used in the light beam tracking receiver shown in FIG.

3 (a) is a schematic side view of a light beam tracking reception system, and FIG. 3 (b) is a schematic front view of a four-division light receiving element used in the conventional example of FIG. 3 (a). It is.

[Explanation of symbols]

 1, mirror 3 lens 4 optical receiver 5 signal output terminal 6 drive circuit 7 X direction angle signal output terminal 8 Y direction angle signal output terminal 11 light receiving surface of light receiving element 21 reception level input terminal 22, 23 multiplier 24 oscillator 25 , 26 Low-pass filters 27, 28, 31, 32 Adders 29, 30 Amplifiers 33 X-direction control input terminal 34 Y-direction control input terminal 35 X-direction control output terminal 36 Y-direction control output terminal 41 Lens 42 Four-divided light receiving Element 42a-42d Light receiving element 43-46 Output electrode 47 Earth electrode 48 Optical axis

Claims (2)

(57) [Claims] 1. A light beam tracking reception system that detects an angular deviation of incident reception light and generates a tracking signal, wherein: a diameter of a condensed spot where the received light is condensed; and a circular shape of a light receiving element that receives the condensed spot. A light receiving unit having a light receiving surface having substantially the same diameter as a light receiving surface , a condensed spot rotating driving unit for rotating the condensed spot in a circle on a circumference substantially equidistant from the center of the light receiving surface of the light receiving element, A collection for controlling the center of rotation to move to the center of the light receiving surface of the light receiving element.
A light beam tracking reception system , comprising: a light spot rotation center control unit . 2. A light beam tracking reception system for detecting an angular deviation of incident reception light and generating a tracking signal, wherein the mirror is driven by a two-dimensional control signal to change an emission direction of the incident reception light; The lens receives the condensed spot and receives it as the condensed spot by a lens that condenses the received light passing through the mirror to form a condensed spot and a light receiving element having a light receiving surface having a diameter substantially equal to the diameter of the condensed spot. a light receiver for outputting a reception level signal of the received light is, along with rotating the focusing spot substantially equidistant circumferentially on the circular from the center of the light receiving surface of the light receiving element, the received level signal and the The control signal for controlling the center of rotation of the focused spot to move to the center of the light receiving surface of the light receiving element in response to a posture signal of a light beam tracking reception method. Light beam tracking receiver system characterized by having a resulting mirror driving circuit.