JP2008294967A - Optical reception device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the output level of a high frequency signal for each carrier constant even when OMI for each carrier changes in accordance with the specification of an optical signal. <P>SOLUTION: An optical reception device 11 includes a high frequency amplification circuit 13 for amplifying a high frequency signal by an O/E 12. Furthermore, an output level control circuit 14 is connected to the high frequency amplification circuit 13, and the output level control circuit 14 includes a control analysis circuit 17 which adjusts a gain of the high frequency amplification circuit 13 using a temperature monitor value Vt by a temperature monitor circuit 15 and a photodetection current monitor value Vx by a photodetection current monitor circuit 16. The control analysis circuit 17 then offsets the photodetection current monitor value Vx using an output level offset value Vs and sets the gain of the high frequency amplification circuit 13 using such a photo-detection current offset value Vx'. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical receiver that converts an optical signal into a high-frequency signal and outputs the signal at a constant level.

  In general, there is known an optical receiver including an optical-electric conversion circuit that converts an optical signal into a high-frequency signal and a high-frequency amplifier circuit that amplifies a high-frequency signal by the optical-electric conversion circuit (for example, Patent Document 1). reference). Such an optical receiver includes a temperature monitor circuit that detects (monitors) the ambient temperature around the device and a light-receiving current monitor circuit that monitors the light-receiving current of the optical signal received by the photoelectric conversion circuit. And a control analysis circuit for adjusting the gain of the high-frequency amplifier circuit based on the light reception current monitor value by the light reception current monitor circuit and the temperature monitor value by the temperature monitor circuit. And the output level of the high frequency signal of the optical receiver is kept constant by the control analysis circuit.

JP 2002-33705 A

  By the way, in the optical receiver according to the prior art, the light receiving current of the optical signal received by the photoelectric conversion circuit includes a direct current component used for detecting the light intensity and an alternating current component that becomes a high frequency signal. Since the light reception current monitor circuit uses the direct current component of the light reception current as the light reception current monitor value, the control analysis circuit adjusts the gain of the high frequency amplifier circuit based on the light reception current monitor value and the like, and outputs the output level of the high frequency signal. (Voltage etc.) is kept constant.

  Here, there is an optical link system in which an optical signal includes a plurality of carriers and the overall OMI (Optical Modulation Index) of these carriers is constant. When an optical receiver according to the prior art is applied to this optical link system, it is necessary to set the ratio between the direct current component and the alternating current component of the optical signal corresponding to the OMI for each carrier to a value determined by the channel plan. There is. That is, when the number of carriers increases, the OMI for each carrier decreases, and when the number of carriers decreases, the OMI for each carrier increases. Therefore, the ratio of the direct current component to the alternating current component of the optical signal changes according to the number of carriers.

  On the other hand, in the prior art, the control analysis circuit adjusts the gain of the high-frequency signal based on the light reception current monitor value or the like by the light reception current monitor circuit regardless of the OMI. There was a possibility that the signal output level specification was not satisfied.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to output a high-frequency signal for each carrier even when the OMI for each carrier changes according to the specifications of an optical signal such as a channel plan. An object of the present invention is to provide an optical receiver capable of maintaining a constant level.

  In order to solve the above-described problems, the present invention provides an optical-electric conversion circuit that converts an optical signal into a high-frequency signal, a high-frequency amplification circuit that amplifies a high-frequency signal by the optical-electric conversion circuit, and the optical-electrical conversion. A temperature monitor circuit for monitoring the ambient temperature of the circuit, a received light current monitor circuit for monitoring a received light current of an optical signal received by the photoelectric conversion circuit, a received light current monitor value by the received light current monitor circuit, and the temperature monitor circuit; And a control analysis circuit for adjusting the gain of the high-frequency amplifier circuit so that the output level of the high-frequency signal amplified by the high-frequency amplifier circuit is constant based on the temperature monitor value by .

  The feature of the configuration adopted by the invention of claim 1 is that the control analysis circuit includes a received light current monitor value offset means for offsetting a received light current monitor value of the received light current monitor circuit based on an output level offset value, and The light receiving current monitor value offset means offset by the light receiving current monitor value and the gain setting means for setting the gain of the high frequency amplifier circuit based on the temperature monitor value of the temperature monitor circuit.

  According to a second aspect of the present invention, the gain setting means includes a gain table storing a relationship between the temperature monitor value and the received light current monitor value and the gain value of the high frequency amplifier circuit, the temperature monitor value and the received light current monitor value, Using the received light current table, the first interpolation means for interpolating the gain table and the received light current table using the temperature monitor value by the temperature monitor circuit, and the received light current monitor value by the received light current monitor circuit. And a second interpolation means for interpolating the gain table.

  According to the first aspect of the present invention, the light reception current monitor value offset means offsets the light reception current monitor value of the light reception current monitor circuit based on the output level offset value input from the outside. For this reason, for example, by inputting an output level offset value corresponding to the channel plan (number of carriers), the received light current monitor value can be converted into a received light current offset value corresponding to the reference channel plan. It is possible to compensate for the variation in OMI for each carrier accompanying the change. And since the gain setting means sets the gain of the high-frequency amplifier circuit based on the received light current monitor value after the offset (light received current offset value) and the temperature monitor value of the temperature monitor circuit, even when the channel plan is changed, The output level of the high frequency signal for each carrier can be kept constant.

  According to the second aspect of the present invention, the gain setting means has a gain table storing the relationship between the temperature monitor value and the received light current monitor value and the gain value of the high frequency amplifier circuit, and the relationship between the temperature monitor value and the received light current monitor value. , A first interpolation means for interpolating the gain table and the light reception current table using the temperature monitor value, and a second interpolation means for interpolating the gain table using the light reception current monitor value. Since the configuration is adopted, the number of data of the temperature monitor value, the received light current monitor value, and the gain value of the high frequency amplifier circuit stored in the gain table can be reduced. For this reason, the storage capacity for the gain table can be reduced, and the data acquisition time can be reduced.

  Hereinafter, an example in which the optical receiver according to the embodiment of the present invention is applied to an optical link CATV (cable television) will be described in detail with reference to the accompanying drawings.

  First, FIG. 1 shows an optical link system to which an embodiment of the invention is applied. The optical link system includes an optical transmitter 1 that converts a high-frequency signal into an optical signal, and an optical receiver that converts the optical signal into a high-frequency signal. The apparatus 11 is configured by an optical transmission path 21 that connects the optical transmitter 1 and the optical receiver 11.

  The optical transmission device 1 includes a transmission-side high-frequency amplifier circuit 2 that amplifies a high-frequency signal, and an electro-optical conversion circuit 3 (hereinafter referred to as E / O3) that converts the high-frequency signal amplified by the high-frequency amplifier circuit 2 into an optical signal. And. At this time, the E / O 3 is connected to the optical transmission line 21 such as an optical fiber and has a laser diode (not shown) for outputting an optical signal, and is directed to the optical transmission line 21 using the laser diode. Output an optical signal.

  Further, the optical modulation degree control circuit 4 is connected to the E / O 3, and the optical modulation degree control circuit 4 monitors the optical modulation degree of the laser diode and controls the gain of the high-frequency amplifier circuit 2 based on the monitoring result. To do. At this time, the optical modulation degree control circuit 4 includes a temperature compensation circuit 5 and a bias current monitor circuit 6. The temperature compensation circuit 5 detects the environmental temperature of the optical transmitter 1 including the E / O 3 and keeps the gain of the high-frequency amplifier circuit 2 constant even when the environmental temperature varies. On the other hand, the bias current monitor circuit 6 monitors the bias current of the laser diode in the E / O 3 and gains the high-frequency amplifier circuit 2 so as to input a high-frequency signal following the conversion efficiency of the laser diode to the E / O 3. To control.

  The optical receiving device 11 has a light receiving element such as a photodiode, for example, and converts an optical signal into a high frequency signal (hereinafter referred to as O / E12), and a high frequency signal converted by the O / E12. And a high frequency amplifier circuit 13 on the receiving side. At this time, the O / E 12 is connected to the optical transmission line 21 and receives an optical signal from the optical transmission line 21.

  Further, an output level control circuit 14 is connected to the O / E 12, and the output level control circuit 14 monitors the reception level of the optical signal received by the light receiving element of the O / E 12, and a high frequency amplification is performed based on the monitoring result. The high frequency output level of the circuit 13 is controlled. At this time, the output level control circuit 14 includes a temperature monitor circuit 15, a received light current monitor circuit 16, and a control analysis circuit 17. The temperature monitor circuit 15 monitors the ambient temperature of the optical receiver 11 including the O / E 12, and outputs a temperature monitor value Vt including an electrical signal such as a voltage corresponding to the ambient temperature.

  On the other hand, the light reception current monitor circuit 16 monitors the light reception current flowing through the light receiving element in the O / E 12. The light reception current monitor circuit 16 outputs a light reception current monitor value Vx including an electric signal such as a voltage corresponding to the detection value of the light reception current.

  Furthermore, the control analysis circuit 17 uses the gain adjustment program shown in FIG. 2 to determine that the output level of the high frequency signal from the high frequency amplifier circuit 13 is constant based on the monitoring results of the temperature monitor circuit 15 and the received light current monitor circuit 16. Thus, the gain of the high frequency amplifier circuit 13 is adjusted.

  Further, as shown in FIG. 3, for example, the control analysis circuit 17 stores a relationship between the temperature monitor value Vt and the received light current monitor value Vx and the applied voltage value Vy corresponding to the gain value of the high frequency amplifier circuit 13. A gain table Ty [i] [j] is provided. At this time, i represents an argument (parameter) of the temperature monitor value Vt, and j represents an argument of the received light current monitor value Vx. Further, the gain table Ty [i] [j] is an optimum applied voltage that makes the output level of the high-frequency signal constant when, for example, the temperature monitor value Vt and the received light current monitor value Vx are changed to various values. The value Vy is obtained by experimentally measuring in advance. For this reason, the argument i is a value (natural number) in the range from the minimum value 0 (zero) to the maximum value Ni, for example, corresponding to the number of data of the temperature monitor value Vt measured in advance. Similarly, the argument j is a value (natural number) in the range from the minimum value 0 (zero) to the maximum value Nj, for example, corresponding to the number of data of the light reception current monitor value Vx measured in advance.

  Therefore, the control analysis circuit 17 determines the applied voltage value Vy using the gain table Ty [i] [j] by determining the arguments i and j based on the temperature monitor value Vt and the received light current monitor value Vx. can do. Therefore, the control analysis circuit 17 includes a temperature table Tt [i] (where 0 ≦ i <Ni) for determining the argument i of the temperature monitor value Vt, and determines the argument j of the received light current monitor value Vx. A two-dimensional light receiving current table Tx [i] [j] (where 0 ≦ i <Ni, 0 ≦ j <Nj).

  Further, in order to set the applied voltage value Vy with high accuracy with respect to the temperature monitor value Vt and the received light current monitor value Vx, the gain table Ty [i] [j] and the received light current table Tx [i] [j] The number of data needs to be increased. However, when the number of data in each table Ty [i] [j], Tx [i] [j] increases, there is a problem that these storage capacities increase and an expensive memory or the like is required.

  Therefore, the control analysis circuit 17 according to the present embodiment interpolates the gain table Ty [i] [j] and the received light current table Tx [i] [j] using the temperature monitor value Vt from the temperature monitor circuit 15. The gain table Ty [i] [j] is interpolated using the received light current monitor value Vx (actually, the received light current offset value Vx ′ after offset) by the received light current monitor circuit 16. Specifically, the received light current table Tx [i] [j] and the gain table Ty [i] [j] are interpolated using the temperature monitor value Vt, and the received light current table Tx ′ [j corresponding to the temperature monitor value Vt. ] And the gain table Ty ′ [j]. Thereafter, the applied voltage value Vy is calculated using the light reception current monitor value Vx and the tables Tx ′ [j], Ty ′ [j].

  The control analysis circuit 17 receives an output level offset value Vs from the outside. At this time, the output level offset value Vs is set so as to correct the difference between the OMI for each carrier in the actual channel plan and the OMI for each carrier in the reference channel plan.

  Specifically, it is as follows. First, as an example, consider a case where an optical signal for CATV includes analog channel and digital channel carriers as shown in FIG. At this time, if the total OMI is m, the OMI for each carrier is mi, and the number of carriers is N, the following relationship is established.

  Here, under the condition that the total OMI is constant, mi increases as the number of carriers N increases, and mi increases as the number of carriers N decreases. That is, mi changes according to the channel plan that determines the number of carriers. On the other hand, mi (OMI for each carrier) is determined by the ratio (mi = Iac / 2Idc) between the AC component Iac and the DC component Idc of the optical signal as shown in FIG. On the other hand, the light reception current monitor circuit 16 monitors the light reception current by using the direct current component Idc of the optical signal, and the control analysis circuit 17 performs the operation of the high frequency amplification circuit 13 according to the light reception current monitor value Vx of the light reception current monitor circuit 16. Adjust the gain. For this reason, when the output level offset value Vs is not input, the gain of the high-frequency amplifier circuit 13 is constant regardless of mi, so that the output level of the high-frequency signal for each carrier varies with mi.

  Therefore, in this embodiment, the output level offset value Vs is set according to the channel plan (OMI for each carrier), and the output level (voltage value) of the high-frequency signal for each carrier is used by using this output level offset value Vs. ) Is kept constant. Specifically, the control analysis circuit 17 generates a gain table Ty [i] [j] for keeping the output level of the high-frequency signal for each carrier constant with respect to the optical signal of the reference channel plan (reference mi). Prepare. In addition, when the actual channel plan is different from the reference channel plan, the received light current monitor value Vx is offset so that mi matches the reference channel plan. That is, for example, when the number of carriers N is large and mi is half that of the reference channel plan, the received light current monitor value Vx is offset by half using the output level offset value Vs. When the number of carriers N is small and mi is twice that of the reference channel plan, the received light current monitor value Vx is offset twice using the output level offset value Vs.

  The optical receiver 11 according to the present embodiment has the above-described configuration. Next, a gain adjustment program for the high-frequency amplifier circuit 13 by the optical receiver 11 will be described with reference to FIGS. 1 and 2.

  First, in step 1, the temperature monitor value Vt output from the temperature monitor circuit 15 is read. Next, in step 2, it is determined whether or not the temperature monitor value Vt is smaller than the minimum value Tt [0] of the temperature table Tt [i] (Vt <Tt [0]). At this time, the temperature table Tt [i] is configured to increase in value as the argument i increases (Tt [0] <Tt [1] <... <Tt [Ni]). If “YES” is determined in step 2, the temperature monitor value Vt is smaller than the minimum value Tt [0] of the temperature table Tt [i] stored in advance in the control analysis circuit 17. Then, the argument m of the temperature table Tt [i] is set to the minimum value 0 (zero) (m = 0).

  On the other hand, if “NO” is determined in step 2, the process proceeds to step 4 and whether or not the temperature monitor value Vt is equal to or greater than the maximum value Tt [Ni] of the temperature table Tt [i] (Vt ≧ Tt [Ni]). Determine. If “YES” is determined in step 4, the temperature monitor value Vt is equal to or greater than the maximum value Tt [Ni] of the temperature table Tt [i] stored in advance in the control analysis circuit 17. Then, the argument m of the temperature table Tt [i] is set to a value 1 less than the maximum value Ni (m = Ni-1).

  If “NO” is determined in the step 4, the process proceeds to a step 6 to determine an argument m satisfying the following expression (2).

  Then, after the argument m is determined in any one of steps 3, 5, and 6, the process proceeds to steps 7 and 8, and the first interpolation process based on the temperature monitor value Vt is performed. Specifically, in step 7, the received light current table Tx ′ [j] at the temperature monitor value Vt is created based on the following equation (3). At this time, the light reception current table Tx ′ [j] is configured such that the value decreases as the argument j increases (Tx ′ [0]> Tx ′ [1]>...> Tx ′ [Nj] ).

  Next, in step 8, a gain table Ty ′ [j] indicating the relationship between the received light current at the temperature monitor value Vt and the applied voltage value of the high-frequency amplifier circuit 13 is created based on the following equation (4). At this time, the gain table Ty ′ [j] is configured to increase in value as the argument j increases (Ty ′ [0] <Ty ′ [1] <... <Ty ′ [Nj]). .

  At this time, the equations 3 and 4 indicate that the temperature monitor value Vt is a value between the minimum value Tt [0] and the maximum value Tt [Ni] of the temperature table Tt [i] (Tt [0] ≦ Vt < In the case of Tt [Ni]), the linear interpolation formula is used. In other cases, the linear extrapolation formula is used. If the temperature range of the temperature table Tt [i] is expanded, it is possible to perform linear interpolation for all temperatures. However, in this case, it takes a long time to acquire the gain table Ty [i] [j] and the like, and productivity is lowered. Therefore, the gain table Ty [i] [j] is acquired for the normal temperature range when the optical receiver 11 is used, and the temperature range other than this is compensated by linear extrapolation.

  Next, in step 9, the received light current monitor value Vx output from the received light current monitor circuit 16 is read. In step 10, the output level offset value Vs input from the outside is read. In step 11, monitor current value offset processing is performed based on the following equation (5) to calculate a received light current offset value Vx ′ obtained by offsetting the received light current monitor value Vx.

  However, the unit of the light reception current monitor value Vx and the light reception current offset value Vx ′ is ampere [A], and the unit of the output level offset value Vs is decibel [dB]. Further, when calculating the light receiving current offset value Vx ′, it cannot be processed by the four arithmetic operations as shown in the equation (5), and there is a possibility that the calculation burden is heavy. In this case, in order to reduce the burden of calculation processing, a table for converting the output level offset value Vs to the calculation value Cs is prepared, and the received light current offset value Vx ′ is calculated using this conversion table. Good.

  Next, in step 12, it is determined whether or not the received light current offset value Vx ′ is larger than the maximum value Tx ′ [0] of the received light current table Tx ′ [j] (Vx ′> Tx ′ [0]). If “YES” is determined in step 12, the light reception current offset value Vx ′ is larger than the maximum value Tx ′ [0] of the light reception current table Tx ′ [j]. The argument n of Tx ′ [j] is set to the minimum value 0 (zero) (n = 0).

  On the other hand, if “NO” is determined in step 12, the process proceeds to step 14, where the light reception current offset value Vx ′ is equal to or less than the minimum value Tx ′ [Nj] of the light reception current table Tx ′ [j] (Vx ′ ≦ Tx ′). [Nj]). If “YES” is determined in step 14, the light reception current offset value Vx ′ is equal to or less than the minimum value Tx ′ [Nj] of the light reception current table Tx ′ [j]. The argument n of the current table Tx ′ [j] is set to a value 1 less than the maximum value Nj (n = Nj−1).

  If “NO” is determined in step 14, the process shifts to step 16 to determine an argument n that satisfies the following expression (6).

  Then, after the argument n is determined in any one of Steps 13, 15, and 16, the process proceeds to Step 17 to perform the second interpolation process based on the light reception current offset value Vx ′ (light reception current monitor value Vx). Specifically, the applied voltage value of the high-frequency amplifier circuit 13 is calculated based on the following formula 7 using the received light current offset value Vx ′, the received light current table Tx ′ [j], and the gain table Ty ′ [j]. Vy is calculated.

  At this time, the equation (7) indicates that the received light current offset value Vx ′ is a value (Tx ′ [0] between the maximum value Tx ′ [0] and the minimum value Tx ′ [Nj] of the received light current table Tx ′ [j]. ] ≧ Vx ′> Tx ′ [Nj]), a linear interpolation formula is used, otherwise a linear extrapolation formula is used. Further, in order to shorten the acquisition time of the gain table Ty [i] [j], etc., the gain table Ty [i] [j] is acquired for the range of the received light current monitor value Vx that is normally received by the optical receiver 11; The other range is compensated by linear extrapolation. Then, after step 17 is completed, the processing after step 1 is repeated.

  The optical receiver 11 according to the present embodiment executes the above-described gain adjustment program, and its operation will be described in detail as follows.

  First, an output level offset value Vs is set according to the channel plan, and this output level offset value Vs is output to the control analysis circuit 17. When the optical signal transmitted from the optical transmission line 21 by the O / E 12 is received, the received light current monitor circuit 16 monitors the direct current component Idc of the optical signal as the received light current, and the received light current monitor value corresponding to the direct current component Idc. Vx is output to the control analysis circuit 17. Further, the temperature monitor circuit 15 outputs a temperature monitor value Vt corresponding to the ambient temperature of the optical receiver 11 to the control analysis circuit 17.

  At this time, the control analysis circuit 17 uses the equations 3 and 4 to interpolate the two-dimensional gain table Ty [i] [j] with respect to the temperature using the temperature monitor value Vt. A table Tx ′ [j] and a gain table Ty ′ [j] are created. As a result, as indicated by triangles in FIG. 3, data corresponding to the temperature monitor value Vt (light reception current table Tx ′ [j] and gain table) is stored between the data of the gain table Ty [i] [j] stored in advance. Ty ′ [j]) is created.

  Next, the control analysis circuit 17 offsets the received light current monitor value Vx using the output level offset value Vs, and calculates the received light current offset value Vx ′. Thereby, the difference between the OMI for each carrier in the actual channel plan and the OMI for each carrier in the reference channel plan can be corrected.

  Finally, the control analysis circuit 17 uses the equation (7) to perform high-frequency amplification in order to interpolate the two-dimensional gain table Ty [i] [j] with respect to the light receiving current using the light receiving current offset value Vx ′. An applied voltage value Vy of the circuit 13 is calculated. As a result, as indicated by a cross in FIG. 3, the gain value (applied voltage) corresponding to the temperature monitor value Vt and the received light current offset value Vx ′ from the gain table Ty [i] [j] stored in advance in the reference channel plan. The value Vy) can be calculated.

  Thus, in the present embodiment, the control analysis circuit 17 offsets the light reception current monitor value Vx of the light reception current monitor circuit 16 based on the output level offset value Vs from the outside. Therefore, for example, by inputting the output level offset value Vs corresponding to the channel plan, the received light current monitor value Vx can be converted into a received light current value (received current offset value Vx ′) corresponding to the reference channel plan. Thus, it is possible to compensate for the variation in OMI for each carrier accompanying the change of the channel plan. Since the control analysis circuit 17 sets the gain of the high-frequency amplifier circuit 13 based on the received light current offset value Vx ′ and the temperature monitor value Vt, the output level of the high-frequency signal for each carrier even when the channel plan is changed. (Amplitude of the voltage of the high-frequency signal per carrier) can be kept constant.

  Further, since the control analysis circuit 17 offsets the received light current monitor value Vx based on the output level offset value Vs, it is not necessary to provide a hardware offset circuit separately on the output side of the high frequency signal, for example. It is possible to cope with a change in channel plan by processing. For this reason, it can be easily applied to an existing optical receiver. Furthermore, since the control analysis circuit 17 collectively performs offset processing by changing the channel plan and gain adjustment processing by the received light current and temperature, it is manufactured as compared with the case where a circuit for processing these separately is provided. Cost can be reduced.

  The control analysis circuit 17 also stores a gain table Ty [i] [j] storing the relationship between the temperature monitor value Vt and the received light current monitor value Vx and the gain value of the high frequency amplifier circuit 13, the temperature monitor value Vt and the received light current. A light receiving current table Tx [i] [j] storing the relationship with the monitor value Vx, and using the temperature monitor value Vt, a gain table Ty [i] [j] and a light receiving current table Tx [i] [j] , And the gain table Ty [i] [j] is interpolated using the light reception current monitor value Vx (light reception current offset value Vx ′). Therefore, the temperature monitor value Vt, the received light current monitor value Vx, and the gain value (applied voltage value Vy) of the high frequency amplifier circuit 13 stored in the gain table Ty [i] [j] and the received light current table Tx [i] [j]. Therefore, the storage capacity for each table Ty [i] [j], Tx [i] [j] can be reduced. Further, even when data of each table Ty [i] [j], Tx [i] [j] is experimentally acquired, the data acquisition time can be reduced and productivity can be increased.

  In the above embodiment, step 11 in FIG. 2 shows a specific example of the received light current monitor value offset means, and steps 1 to 10 and steps 12 to 17 show a specific example of the gain setting means. Moreover, in the said embodiment, steps 2-8 in FIG. 2 show the concreteness of the 1st interpolation means, and steps 12-17 show the concrete example of the 2nd interpolation means.

  In the above embodiment, the optical receiver 11 is applied to the optical link CATV. However, the present invention is not limited to this. For example, the optical receiver 11 is an ROF (Radio on Fiber) that relays a radio signal using an optical fiber. It is good also as composition to apply.

It is a block diagram which shows the optical link system using the optical receiver by embodiment of this invention. It is a flowchart which shows the gain adjustment program by the control analysis circuit in FIG. It is explanatory drawing which shows the gain table memorize | stored in the control analysis circuit in FIG. It is explanatory drawing which shows the carrier used for CATV. It is a characteristic diagram which shows the intensity | strength of the optical signal with respect to time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Optical receiver 12 Opto-electric conversion circuit 13 High frequency amplifier circuit 14 Output level control circuit 15 Temperature monitor circuit 16 Light reception current monitor circuit 17 Control analysis circuit

Claims (2)

An opto-electric conversion circuit for converting an optical signal into a high-frequency signal;
A high frequency amplifier circuit for amplifying a high frequency signal by the photoelectric conversion circuit;
A temperature monitoring circuit for monitoring the ambient temperature of the photoelectric conversion circuit;
A light receiving current monitor circuit for monitoring a light receiving current of an optical signal received by the photoelectric conversion circuit;
Based on the light reception current monitor value by the light reception current monitor circuit and the temperature monitor value by the temperature monitor circuit, the gain of the high frequency amplifier circuit is adjusted so that the output level of the high frequency signal amplified by the high frequency amplifier circuit is constant. In an optical receiver including a control analysis circuit for
The control analysis circuit includes: a received light current monitor value offset means for offsetting a received light current monitor value of the received light current monitor circuit based on an output level offset value; a received light current monitor value offset by the received light current monitor value offset means; An optical receiver comprising: gain setting means for setting a gain of the high-frequency amplifier circuit based on a temperature monitor value of the temperature monitor circuit.   The gain setting means includes a gain table storing a relationship between the temperature monitor value and the received light current monitor value and a gain value of the high frequency amplifier circuit, and a received light current storing a relationship between the temperature monitor value and the received light current monitor value. A table, first interpolation means for interpolating the gain table and the received light current table using the temperature monitor value by the temperature monitor circuit, and the gain table is interpolated using the received light current monitor value by the received light current monitor circuit The optical receiver according to claim 1, comprising a second interpolation unit.

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