JP2008135821A - Optical transmission system - Google Patents

Abstract

Transmission / reception in an optimum state is possible regardless of the state of an optical transmission section.
A transmission unit 41 of a transmission station 2 includes an electric / optical conversion unit 15, an input level adjustment unit 47 that adjusts an input level to the electric / optical conversion unit, and a transmission station control unit 43 that controls the level adjustment. And the receiving unit 44 of the receiving station 3 includes the optical / electrical converter 22, the CN characteristic detecting means 52 for detecting either the signal strength of the CN characteristic or the distortion from the received signal, A gain correction unit 51 that adjusts the gain of the signal from the optical / electric conversion unit and a receiving station control unit 46 that controls the adjustment of the gain are provided, and the detected CN characteristic is the transmitting unit 45 of the receiving station. The transmission station controller adjusts the input level via the input level adjustment means based on CN characteristics, and transmits input level adjustment information to the reception station. The controller is based on the input level adjustment information. Configured as to adjust the gain through come said gain correcting means.
[Selection] Figure 1

Description

  The present invention relates to an optical transmission system in which optimum optical transmission characteristics can be obtained in various optical line environments.

  First, referring to FIG. 4, an outline of a conventional optical transmission system will be described.

  In FIG. 4, 1 is a base transceiver station (BTS: Base Transceiver Station), 2 is a master station device, 3 is a slave station device, 4 is an antenna, 5 is a portable device, and the base station wireless transceiver Signals are transmitted and received between the device 1 and the master station device 2 by radio or cable, and the master station device 2 and the slave station device 3 are connected by optical transmission paths 7 and 8 represented by optical fibers, Signals are transmitted and received between the station device 3 and the portable device 5 via the antenna 4.

  FIG. 5 shows a schematic configuration of the master station device 2 and the slave station device 3. The master station device 2 has a master station transmitter 9 and a master station receiver 10, and the slave station device 3 is a slave station. It has a receiver 11 and a slave station transmitter 12.

  The master station transmitting unit 9 includes an input unit 13 to which a radio high-frequency signal (RF signal) from the base station radio transceiver 1 is input, an amplifying unit 14 for amplifying the input RF signal, and from the amplifying unit 14 A master station power / light converting unit (for example, laser diode: LD) 15 that modulates and outputs the light intensity with the RF signal is provided.

  The master station receiving unit 10 photoelectrically converts an optical signal transmitted from the slave station device 3 via the optical transmission path 8 on an uplink (a line on which a signal is transmitted from the slave station toward the master station). A master optical / electrical converter (for example, photodiode: PD) 16, an amplifier 17 for amplifying the converted electric signal, a variable attenuator 18 for correcting the loss of the optical transmission line 8, an amplifier 19, and an output unit 20 It has.

  The slave station receiver 11 is a slave optical / electric converter (e.g., photodiode: PD) 22 that converts an optical signal on a downlink (a line on which a signal is transmitted from the master station to the slave station) into an electrical signal. , An amplifying unit 23, a variable attenuator 24 for correcting loss in the optical transmission line 7 in the downlink, an amplifying unit 25, and an output unit 26 for sending the downlink RF signal to the antenna 4.

  The slave station transmitter 12 includes an input unit 27 that receives an RF signal from the portable device 5, an amplifier 28, and a slave station power / optical converter (for example, a laser diode) that converts an uplink electrical signal into an optical signal. LD) 29.

  In the downlink, an RF signal input from the input unit 13 is amplified by the amplification unit 14, converted into an analog optical signal by the master station power / optical conversion unit 15, and the optical signal is transmitted through the optical transmission line 7. It is transmitted to the slave station device 3.

  In the slave station device 3, the received optical signal is converted into an electrical signal by the slave station optical / electrical converter 22, and the amplifier 23 converts the electrical signal into a required carrier-to-noise ratio (C / N: Carrier Noise). Amplification is performed so that (Ratio) can be secured. The variable attenuator 24 corrects the loss of the optical transmission line 7, and the amplifying unit 25 amplifies the RF signal to a predetermined power and radiates it through the antenna 4 to secure a service area.

  On the uplink, the RF signal of the portable device 5 is received via the antenna 4, and the received RF signal is input to the amplification unit 28 via the input unit 27 and amplified by the amplification unit 28. . Further, it is converted into an analog optical signal by the slave station power / optical converter 29, and the optical signal is transmitted to the master station device 2 through the optical transmission line 8.

  In the master station device 2, the optical signal is converted into an electrical signal by the master station optical / electric converter 16, and the electrical signal is amplified by the amplifier 17. The variable attenuator 18 corrects the loss in the optical transmission line 8, amplifies it to a level necessary for reception in the amplifier 19, and transmits it from the output unit 20 to the base station radio transceiver 1. . The uplink and downlink are substantially symmetric.

  FIG. 6 shows a main part of the master station light / electric converter 16 and the slave station light / electric converter 22, in FIG. 6, 31 is a photodiode, and 32 is for cutting a DC component. A capacitor 33 is a resistor for converting the current value of the photodiode into a voltage, and 34 is an ALM determination unit for identifying ALM (ALARM) from the voltage value.

  When the photodiode 31 receives light, a current is generated, converted into a voltage by the resistor 33, a direct current component is cut by the capacitor 32, and an electric (RF) signal is output through the capacitor 32.

  The amount of current I generated by the photodiode 31 is proportional to the amount of received light (optical power) P. When the amount of received light P increases, the amount of current I increases, and when the amount of received light P decreases, the amount of current I decreases. Therefore, a voltage having a magnitude corresponding to the amount of light received by the photodiode 31 is input to the ALM determination unit 34.

  Each of the ALM determination units 34 has a threshold value, detects the light reception level, determines whether the light reception level is equal to or higher than the threshold value, and determines whether or not the light reception level is equal to or higher than the threshold value, and ALM is generated.

  In the conventional optical transmission system described above, the logarithmic value of the loss amount in the optical section increases in proportion to the distance. Therefore, the amount of loss varies depending on the length of the optical section. Further, the characteristic content of signal degradation varies depending on the amount of loss in the optical section.

  When the optical loss is large, the carrier 36 is buried in the noise floor (noise level) 37 as shown in FIG. 7A, so that the C / N is deteriorated. On the other hand, when the loss in the optical section is small, the noise floor 37 becomes small with respect to the carrier 36 as seen in FIG. Distortion 57 caused by modulation or the like cannot be ignored and restricts signal quality.

  Conventionally, even if the loss amount in the optical transmission section is large, the noise level is within the standard, and even if the loss amount in the optical transmission section is small, the distortion level is within the standard. The output value of the light conversion unit 15 and the attenuation factor of the variable attenuator 24 are set.

  For this reason, the conventional optical transmission system can perform optical communication within the specified range, but it cannot be said that the communication state is in an optimum state, and the performance of the optical transmission system is not sufficiently exhibited.

JP 2003-298526 A

  In view of such a situation, the present invention enables transmission / reception in an optimum state regardless of the state of the optical transmission section, so that the performance of the optical transmission system is fully exhibited.

  The present invention provides an optical transmission system that performs optical transmission between a plurality of stations each having a transmission unit and a reception unit. The transmission unit of the transmission station includes an electric / optical conversion unit, and the electric / optical conversion unit. It has an input level adjusting means for adjusting the input level and a transmitting station control unit for controlling the level adjustment. The receiving unit of the receiving station is an optical / electric converting unit, and the inner signal strength of the CN characteristic from the received signal ( CN characteristic detection means for detecting either the light reception level) or distortion, gain correction means for adjusting the gain for the signal from the optical / electric conversion section, and a receiving station control section for controlling gain adjustment And the CN characteristic detected by the CN characteristic detecting means is transmitted to the transmitting station via the transmitting section of the receiving station, and the transmitting station control section is configured to transmit the CN characteristic via the input level adjusting means based on the CN characteristic. Adjusting the input level to the photoelectric converter , To send the level adjustment information to the receiving station, the receiving station control unit is one of the optical transmission system configured as to adjust the gain through the gain correction means based on the input level adjustment information.

  According to the present invention, in an optical transmission system that performs optical transmission between a plurality of stations each including a transmission unit and a reception unit, the transmission unit of the transmission station includes an electric / optical conversion unit, and the electric / optical conversion unit. Input level adjusting means for adjusting the input level to the transmitter and a transmitting station control unit for controlling the level adjustment. The receiving unit of the receiving station is an optical / electrical converter, and the signal strength of the CN characteristic is determined from the received signal. CN characteristic detecting means for detecting either the light receiving level or the distortion, gain correcting means for adjusting the gain for the signal from the optical / electrical converter, and receiving station control for controlling the gain adjustment And the CN characteristic detected by the CN characteristic detecting means is transmitted to the transmitting station via the transmitting section of the receiving station, and the transmitting station control section passes the input level adjusting means based on the CN characteristic. Adjust the input level to the electrical / optical converter. At the same time, the input level adjustment information is transmitted to the receiving station, and the receiving station control unit is configured to adjust the gain via the gain correction means based on the input level adjustment information. Regardless of the above, the balance between the distortion level and the noise floor level can be improved, the C / N of the optical transmission system can be improved, and the C / N corresponding to the individual difference of the electric / optical conversion unit can be obtained. As a result, it is possible to alleviate restrictions on the electric / optical converter used, and to achieve excellent effects such as an improvement in yield and a reduction in manufacturing cost.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  A schematic configuration of an optical transmission system according to the present invention will be described with reference to FIG.

  In FIG. 1, the same components as those shown in FIG.

  The master station device 2 includes a master station transmitter 41, a master station receiver 42, and a master station controller 43, and the slave station device 3 includes a slave station receiver 44, a slave station transmitter 45, and a slave station controller 46. is doing.

  The master station transmitter 41 is a master station power / optical converter 15 comprising an input level adjusting variable attenuator 47 as an input level adjusting means, an RF signal amplifying unit 14, a laser diode (LD) and the like. The master station receiver 42 includes a master optical / electric converter 16, an amplifying unit 17, a variable attenuator 18, and an amplifying unit 19 made of a photodiode (PD).

  The master station controller 43 extracts a feedback signal from a slave station included in the electrical signal converted by the master optical / electric converter 16 and demodulates it to a required electrical signal. (MDEM) 48, a master station calculation processing unit 49 that controls the amount of attenuation of the input level adjusting variable attenuator 47 based on information from the master station signal demodulation unit 48, and the master station calculation processing unit 49 A master station signal modulation unit (MMOD) 50 that receives information on the attenuation amount from the signal, performs signal processing such as modulation, and superimposes the signal on the RF signal.

  The slave station receiver 44 includes a slave station optical / electric converter 22 composed of a photodiode (PD) for converting an optical signal input via the optical transmission path 7 into an electrical signal, and the converted electrical signal. An amplifying unit 23, a variable attenuator 24, a gain correcting variable attenuator 51 as a gain correcting means, and an amplifying unit 25. The slave station transmitting unit 45 includes an amplifying unit 28, a laser diode (LD) and the like. A slave station power / optical converter 29 is provided.

  The slave station control unit 46 detects the CN characteristic information of the transmitted signal, for example, the level of distortion, and extracts and demodulates the attenuation information of the master station superimposed on the RF signal. Based on the distortion data and attenuation data from the reception signal processing unit 52, a slave station arithmetic processing unit 53 that controls the attenuation amount of the reception signal processing unit 52, and the distortion data is modulated and superimposed on the signal transmitted to the master station And a slave station signal modulator (SMOD) 54.

  Next, the operation of the optical transmission system will be described with reference to FIG.

  An RF signal is input from the input unit 13 at a required level, and an optical signal converted by the master station power / optical converter 15 is transmitted to the slave station device 3 through the optical transmission line 7.

  The slave station optical / electrical converter 22 converts the optical signal into an electrical signal. The reception signal processor 52 detects the electrical signal from the frequency information through a steep filter and amplifier to detect the distortion level. The detected distortion is input to the slave station calculation processing unit 53, and the slave station calculation processing unit 53 adjusts the attenuation amount of the reception signal processing unit 52 based on the input distortion so as to obtain a predetermined gain. Control (STEP: 01).

  The distortion data is input from the slave station arithmetic processing unit 53 to the slave station signal modulation unit 54, subjected to necessary signal processing such as modulation by the slave station signal modulation unit 54, and transmitted to the master station device 2. Superimposed on the RF signal. The slave station power / light conversion unit 29 performs light-to-light conversion and transmits the light to the master station device 2 through the optical transmission line 8 (STEP: 02).

  The master station optical / electrical converter 16 converts an optical signal into an electrical signal. The master station signal demodulator 48 extracts the slave station distortion information superimposed from the converted electrical signal (STEP: 03), and the slave station distortion information is input to the master station calculation processor 49. The master station arithmetic processing unit 49 adjusts the amount of attenuation of the input level adjusting variable attenuator 47 in a predetermined step based on slave station distortion information. Note that the step size of the attenuation amount with respect to the attenuation amount is set in advance in a data table or the like (STEP: 04).

  By changing the amount of attenuation by the input level adjusting variable attenuator 47, the signal level (intensity) from the master station power / optical converter 15 is changed. The attenuation adjustment data is also output to the master station signal modulation unit 50, and the master station signal modulation unit 50 performs necessary signal processing such as modulation, superimposed on the RF data, and transmitted to the slave station device 3. (STEP: 05, STEP: 06).

  The signal transmitted via the optical transmission line 7 is converted into an electrical signal by the slave station optical / electrical conversion unit 22, and the received signal processing unit 52 converts adjusted attenuation amount data at the master station from the transmitted signal. (STEP: 07), and the slave station calculation processing unit 53 adjusts the attenuation amount of the gain correction variable attenuator 51 so as to correspond (cancel) to the extracted adjustment attenuation amount (STEP: 08). .

  It is determined whether the distortion of the electric signal obtained by adjusting the attenuation amount of the received signal processing unit 52 is larger or smaller than the threshold value. If the distortion is larger, the attenuation amount control is further repeated (STEP 09). .

  By adjusting the input level to the LD according to the present invention and adjusting the distortion characteristics of the optical transmission system, when the loss in the optical transmission section is large, the attenuation of the input level adjusting variable attenuator 47 is controlled to be small. Is done. As a result, as shown by the broken line in FIG. 7A, the distortion 57 is deteriorated, but the noise floor 37 is lowered, and as a whole, the carrier 36 becomes larger (indicated by E in the figure), and C / N Will improve.

  When the loss amount in the optical transmission section is small, the attenuation amount of the input level adjusting variable attenuator 47 is controlled to be large. As a result, as shown by the broken line in FIG. 7B, the noise floor 37 rises, but the distortion 57 is improved, and the carrier 36 becomes larger as a whole (indicated by E in the figure), C / N is improved.

  Thus, the input level to the LD is optimized, the distortion characteristics of the optical transmission system are optimized, and a transmission / reception state optimal for the optical transmission conditions is obtained, so that the performance of the optical transmission system is fully exhibited.

  In addition, according to the control of the transmission / reception conditions, it is possible to adjust the master station device 2 and the slave station device 3 corresponding to individual differences of LDs, thereby relaxing restrictions on the use conditions of the LDs and improving the production yield.

  Next, a case where there are a plurality of slave station devices 3 will be described with reference to FIG.

  FIG. 3 shows a state in which communication is performed between one master station device 2 and n slave station devices 3.

  In this case, since the input level to the master station power / optical converter 15 of the master station device 2 is the same for n slave station devices 3, the master station control unit 43 is connected to each slave station device. 3 is obtained from the distortion information from 3, and the average value of the transmission loss is obtained.

  Based on the average value of transmission loss, the master station control unit 43 sets the attenuation of the input level adjusting variable attenuator 47, and the slave station control unit 46 further adjusts the received signal so as to correspond to the attenuation. The attenuation amount of the processing unit 52 is set.

  By executing the above control, stable optical transmission can be realized even for a plurality of slave station devices 3.

  In the above embodiment, the slave station controller 46 of the slave station device 3 detects the distortion of the optical signal transmitted from the master station device 2, and the detected distortion is transmitted to the master station device 2. Based on the distortion, the adjustment of the input level to the parent station electric / optical converter 15 of the parent station device 2 based on the distortion, and the adjustment of the input level at the parent station are fed back to the child station device 3, and the gain of the child station is After the adjustment, the slave station control unit 46 of the slave station device 3 detects the intensity of the optical signal transmitted from the master station device 2 and determines the detected optical signal strength as the master station. The input level to the master station power / optical converter 15 of the master station device 2 is adjusted based on the intensity of the optical signal detected by the slave station and fed back to the device 2 to adjust the input level at the master station. It may be fed back to the slave station device 3 to adjust the gain of the slave station.

  Further, although the input level adjustment and gain adjustment have been described for the downlink, it goes without saying that the same can be applied to the uplink.

  That is, the receiving side detects either the carrier (signal strength) or noise (distortion) of the CN characteristic of the transmitted optical signal, and the input level to the LD on the transmitting side based on the information of the detected CN characteristic And the gain on the receiving side.

(Appendix)
The present invention includes the following embodiments.

  (Supplementary Note 1) A downlink signal is input and converted into an optical signal, and the downlink signal is distributed and transmitted to a plurality of slave stations by an optical cable, and is transmitted from a plurality of optical transmission slave station devices (hereinafter referred to as slave station devices). An optical transmission master station device (hereinafter referred to as a master station device) having a function of receiving an optically converted upstream signal and combining and outputting an upstream signal of a mobile phone that has been converted into an electrical signal after optical / electrical conversion; Receives the upstream signal from the antenna end as well as the function of receiving the downstream signal converted into the optical signal sent from the station device, converting the input optical signal into an electrical signal, amplifying it to a predetermined power, and outputting it. In the system comprising the slave station device having a function of converting an electrical signal into an optical signal and sending it to the master station device via an optical cable, the intensity of the optical signal from the master station device is detected inside the slave station device. Received light detection circuit section Input level adjusting means capable of determining an optimum input level to the master station device by the control, apparatus gain correcting means for keeping the apparatus gain constant, and control for controlling the input level adjusting means and gain correcting means And an optical transmission system comprising a communication means for exchanging information between stations.

1 is a block diagram showing an optical transmission system according to an embodiment of the present invention. It is a flowchart which shows the effect | action of embodiment of this invention. It is a block diagram which shows another example of embodiment of this invention. It is a block diagram which shows the outline of an optical transmission system. It is a block diagram which shows the conventional optical transmission system. It is explanatory drawing of a main | base station optical / electrical-conversion part and a slave station optical / electrical-conversion part. It is explanatory drawing which shows the relationship between a carrier and a noise floor about the signal transmitted in an optical transmission area, (A) is a case where a noise floor is high, (B) is a case where a noise floor is low.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station radio | wireless transmitter / receiver 2 Master station apparatus 3 Slave station apparatus 7 Optical transmission path 8 Optical transmission path 15 Master station electric / optical conversion part 16 Master station optical / electric conversion part 22 Slave station optical / electrical conversion part 29 Slave station electric / Optical converter 41 master station transmitter 42 master station receiver 43 master station controller 44 slave station receiver 45 slave station transmitter 46 slave station controller 47 input level adjusting variable attenuator 48 master station signal demodulator 49 master Station calculation processing unit 50 Master station signal modulation unit 51 Variable attenuator for gain correction 52 Received signal processing unit 53 Slave station calculation processing unit 54 Slave station signal modulation unit

Claims (1)

  In an optical transmission system that performs optical transmission between a plurality of stations each having a transmission unit and a reception unit, the transmission unit of the transmission station adjusts the electric / optical conversion unit and the input level to the electric / optical conversion unit Input level adjusting means and a transmitting station control unit for controlling the level adjustment, the receiving unit of the receiving station is an optical / electrical converter, and any of the signal strength of the CN characteristic or the distortion from the received signal CN characteristic detecting means for detecting one of the above, a gain correcting means for adjusting a gain of a signal from the optical / electrical converter, and a receiving station controller for controlling gain correction, the CN characteristic detecting CN characteristics detected by the means are transmitted to the transmitting station via the transmitting section of the receiving station, and the transmitting station control section inputs to the electric / optical conversion section via the input level adjusting means based on the CN characteristics. Adjust the level and input level adjustment information Transmitted to the serial receiving station, an optical transmission system, wherein the receiving station control unit configured such that adjusting the gain through the gain correction means based on the input level adjustment information.

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