JP2009141448A - Optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system more appropriately coping with deterioration in transmission quality in a down stream, on the side of an optical transmitter. <P>SOLUTION: The optical transmission system is provided with: one or more optical receivers 20 each having a light receiving means 21 for converting an optical signal into an electric signal, a signal intensity detection means 25 for detecting signal intensity of the optical signal, and a control signal output means 26 for generating and outputting a first control signal C<SB>1</SB>including signal intensity information; and an optical transmitter 10 having an emission element 11 which generates the optical signal, a signal intensity information acquisition means 12 which accepts the first control signal C<SB>1</SB>from an optical receiver 20 which accepts the optical signal, a temperature detection means 13 for detecting temperature of the emission element 11 to generate a second control signal including temperature information R<SB>TEMP</SB>, a driving means for performing current control of the emission element 11 to control intensity of the optical signal based on a current control signal, and control means 12, 15 for generating the current control signal based on the signal intensity information R<SB>BIAS</SB>, R<SB>MOD</SB>. and the temperature information R<SB>TEMP</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical transmission system that performs data communication using optical signals.

  Data communication by the optical transmission system that transmits information via an optical medium such as an optical transmission base station and an optical fiber, the signal degradation in the base station is extremely small compared to the data communication by the electric transmission system, The transmission speed can be made extremely fast, and the transmission capacity is large. For this reason, data communication by the optical transmission method has been conventionally used for applications such as intercontinental long-distance data communication in a telephone communication network, the Internet network, and the like.

  Furthermore, in recent years, in small terminal devices such as personal computers (personal computers), televisions, and mobile phones installed in ordinary houses, transmission speeds have been increased and transmission capacity has been increased. There is a growing need for data communication using optical transmission systems in terminal equipment. More specifically, for example, in a data communication with a personal computer or a TV, a mobile phone equipped with a one-segment support function, the data capacity of video data to be displayed on the display screen has been dramatically increased. A bandwidth of several Gbps is required.

  Further, in data communication using the electric transmission method, radiation noise called EMI (Electromagnetic Interference) is generated. In particular, in mobile phones and the like, radiation noise generated by electrical transmission data communication in the device is relatively large, and the influence on home appliances such as personal computers and televisions cannot be ignored. For this reason, in particular, in devices that generate a relatively large amount of radiation noise, such as a cellular phone, it is required to introduce data communication using an optical transmission method that has a relatively small amount of radiation noise and a relatively low frequency of occurrence. It has become like this.

  As a technique for maintaining transmission quality in optical transmission, for example, in light transmission, a light emitting element (laser module) equipped with a cooling heating element and a temperature sensitive element is used. There is an optical transmission / reception apparatus that performs control to make constant, and performs control to make the wavelength of an optical signal constant in other cases (see, for example, Patent Document 1).

  As another technique for maintaining transmission quality in optical transmission, for example, in the optical transmission from the terminal side optical transceiver to the base station side optical transceiver, the intensity of the voltage signal obtained by converting the received optical signal is increased. Based on this, there is a terminal-side optical transmission / reception device that obtains the distance between the base-station-side optical transmission / reception device and the terminal-side optical transmission / reception device, and adjusts the intensity of the optical signal to be transmitted accordingly (for example, see Patent Document 2). ).

  Furthermore, as a technique for improving the reliability of the optical transmission / reception apparatus in optical transmission, for example, in order to prevent the destruction of the optical transmission light emitting element due to the output from the holding circuit when the optical output is interrupted, A monitor light emitting element is provided in the vicinity, and the light emission intensity of the light transmitting light emitting element (current value or voltage value of the light transmitting light emitting element) is monitored using the monitor light emitting element so that the light emission intensity falls within a predetermined range. In addition, there is an optical transceiver that adjusts the output of the holding circuit (see, for example, Patent Document 3).

  Here, FIG. 13 shows an example of a schematic configuration of an optical transmission system according to the prior art. Here, a case where the base station side optical transmission / reception device 100 is configured to be able to perform data communication with a plurality of terminal side optical transmission / reception devices 200 by an optical transmission method is shown.

  Specifically, the base station side optical transmission / reception device 100 includes an optical transmission device 110 that outputs an optical signal downstream to the optical reception device 210 of the terminal side optical transmission / reception device 200, and a terminal side optical transmission / reception device 200. The optical receiver 120 is configured to receive an optical signal output from the optical transmitter 220 via the upstream.

The optical transmission device 110 detects a signal intensity of the light emitting element 111 that generates an optical signal, and converts the current signal output from the signal intensity detecting light-receiving element 112 into a voltage signal (TIA (Transfer Impedance Amp)). A signal intensity detecting light receiving element 112 that outputs a signal intensity detection result through an AMP circuit that amplifies the voltage signal output from the circuit and the TIA circuit, and a minimum current for the light emitting element 111 to output an optical signal. A driver 114 for controlling a prescribed threshold current I _BIAS and a modulation current I _MOD for modulating an optical signal, driver control means 115 for supplying the threshold current I _BIAS and a modulation current I _MOD to the driver 114, and a signal intensity detection APC that receives the detection result of the signal intensity from the light receiving element 112 and controls the driver control means 115 And Automatic Phase Control) controller 113, and a. Here, the light emitting element 111 is configured using a photodiode.

  The optical receiver 120 includes a light receiving element 121 that converts an optical signal into an electric signal, a TIA circuit 222 that converts an electric signal (current signal) from the light receiving element 121 into a voltage signal, and a voltage signal output from the TIA circuit 222. And an AMP circuit 223 that outputs the signal to the outside.

  The terminal-side optical transceiver 200 receives an optical signal from the optical transmitter 110 of the base station-side optical transceiver 100 via the downstream, and outputs from the optical receiver 120 of the base-station optical transceiver 100. The optical transmission device 220 is configured to receive the received optical signal via the upstream.

  The optical receiver 210 includes a light receiving element 211 that converts an optical signal into an electric signal, a TIA circuit 212 that converts an electric signal (current signal) from the light receiving element 211 into a voltage signal, and a voltage signal output from the TIA circuit 212. An AMP circuit 213 that amplifies the voltage signal, an AMP circuit 214 that amplifies the voltage signal output from the AMP circuit 213 and outputs it to the outside, and the base station side optical transceiver 100 based on the voltage signal output from the AMP circuit 213 Distance estimation means 215 for calculating distance information indicating the distance of light or light attenuation information indicating the amount of light attenuation in the downstream.

The optical transmitter 220 controls the light emitting element 221 that generates the optical signal, the threshold current I _BIAS that defines the minimum current for the light emitting element 111 to output the optical signal, and the modulation current I _MOD for modulating the optical signal. A driver 222 that controls the driver control means 115 based on the distance information or the light attenuation information calculated by the distance estimation means 215, the driver control means 224 that supplies the driver 114 with the threshold current I _BIAS and the modulation current I _MOD Control means 223. Here, the light emitting element 221 is configured using a photodiode.

Japanese Patent Laid-Open No. 11-126940 JP 2005-318269 A JP 2000-269896 A

  As described above, in recent years, data communication based on the optical transmission method has been used for small terminal devices such as mobile phones and the like, and improvement in transmission quality has been demanded.

  However, in the optical transmission / reception apparatuses described in Patent Documents 1 to 3, it is difficult for the optical transmission apparatus to cope with transmission quality degradation in the transmission path (downstream) of the optical signal from the optical transmission apparatus to the optical reception apparatus. It is.

  Specifically, the optical transceiver described in Patent Document 1 performs control to make the wavelength of an optical signal to be transmitted constant based on the temperature condition of the light emitting element, that is, transmission within the optical transceiver on the transmission side. The light emitting element is controlled in consideration of only the conditions. Therefore, the optical transmission / reception device described in Patent Document 1 can cope with the degradation of transmission quality under the transmission conditions inside the device, but copes with the degradation of transmission quality in the transmission path between the optical transmission device and the optical reception device. It is difficult to do.

  In addition, in the optical transmission / reception device described in Patent Document 2, the optical reception device (terminal-side optical transmission / reception device) transmits light from the optical transmission device (base station-side optical transmission / reception device) to the optical reception device (terminal-side optical transmission / reception device). This corresponds to the deterioration of the transmission quality in the signal transmission path (downstream), and the optical transmission device (base station side optical transmission / reception device) cannot cope with the deterioration of the transmission quality in the downstream.

  More specifically, in order to more appropriately cope with the deterioration of transmission quality, the optical transmission device outputs based on the transmission quality deterioration in the transmission path (downstream) from the optical transmission device to the optical reception device. It is desirable to adjust the signal intensity of the optical signal. However, the optical transmission / reception apparatus described in Patent Document 2 is configured such that the terminal-side optical transmission / reception apparatus (optical reception apparatus) adjusts the intensity of the optical signal in response to the deterioration in transmission quality in the downstream. For this reason, the optical transmission / reception apparatus on the base station side (optical transmission apparatus) cannot detect deterioration in transmission quality for any of the downstream and upstream transmission paths. Therefore, even if the base station side optical transmitter / receiver (optical transmitter) constructs the configuration of Patent Document 2, that is, the configuration of adjusting the intensity of the optical signal in response to the deterioration of the transmission quality in the upstream, Since it is impossible to detect transmission quality degradation in the path, it is extremely difficult to adjust the signal strength in consideration of transmission quality degradation in the transmission path.

  That is, the optical transmission / reception device described in Patent Document 2 cannot improve the transmission quality of the optical signal received by the terminal-side optical transmission / reception device (optical reception device). For this reason, in the optical transmission / reception apparatus described in Patent Document 2, it is necessary for the optical transmission apparatus to drive the light emitting element with a certain margin in consideration of the temperature condition of the light emitting element and downstream signal degradation. There was a problem that there was a problem.

  Moreover, the optical transmission / reception apparatus described in Patent Document 3 prevents destruction of the light emitting element, and it is difficult to cope with signal degradation in the transmission path.

  Therefore, there is a demand for an optical transmission system capable of performing data communication by an optical transmission method that can more appropriately cope with a deterioration in transmission quality in the transmission path (downstream and upstream) on the optical transmission device side.

  The present invention has been made in view of the above-described problems, and the object thereof is more appropriate on the optical transmission apparatus side against the deterioration of transmission quality in a transmission path, particularly downstream, in data communication by an optical transmission method. It is in the point which provides the optical transmission system which can respond to this. In addition, the present invention provides an optical transmission apparatus that can more appropriately cope with deterioration of transmission quality in a transmission path, particularly downstream, in data communication using an optical transmission scheme. Furthermore, in data communication using an optical transmission method, an optical receiver having a function of providing information for dealing with deterioration in transmission quality on a transmission path to the optical transmitter is provided. Provided is an optical transmission / reception apparatus capable of controlling a light emitting element appropriately adapted to signal degradation in a transmission-side signal path in data communication by an optical transmission method.

  In order to achieve the above object, an optical transmission system according to the present invention includes a light receiving means for converting an optical signal into an electric signal, a signal intensity detecting means for detecting a signal intensity of the optical signal based on the electric signal, Control signal output means for generating and outputting a first control signal including signal intensity information indicating the signal intensity of the optical signal detected by the signal intensity detection means; A light-emitting element that generates the signal, signal intensity information acquisition means that receives the first control signal from the optical receiver that has received the optical signal, temperature information that detects the temperature of the light-emitting element and indicates the temperature of the light-emitting element Temperature detecting means for generating a second control signal including a driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal, and the signal of the first control signal. Wherein the intensity information on the basis of the temperature information of the second control signal, a first feature in that and a light transmitting device and a control means for generating said current control signal.

  In the optical transmission system according to the present invention having the above-described characteristics, the signal strength detection unit indicates a voltage level of the electrical signal, and a strength determination indicating a predetermined signal strength equal to or higher than the signal strength of the optical signal that can be received by the light receiving unit. A comparison circuit for comparing with a value, and the control signal output means includes a counter for adding when the comparison circuit detects that the voltage level continuously exceeds the intensity determination value for a predetermined period or more, A second feature is that the first control signal is output when the value of the counter exceeds a predetermined first determination value.

  In the optical transmission system according to the present invention having the above characteristics, the optical receiver includes an external input unit that receives the first determination value or an equivalent value that is externally input, and the control signal output unit is externally input. A third feature is that the first determination value is reset based on the first determination value or an equivalent value thereof.

  In the optical transmission system according to the first aspect of the present invention, the signal strength detection unit includes an integration circuit that integrates a voltage level of the electrical signal, and the control signal output unit has a value of the integration circuit, A fourth feature is that the first control signal is output when a predetermined second determination value is exceeded.

  In the optical transmission system according to the present invention having the above characteristics, the optical receiver includes an external input unit that receives the second determination value or an equivalent value that is externally input, and the control signal output unit is externally input. A fifth feature is that the second determination value is reset based on the second determination value or an equivalent value thereof.

  The optical transmission system according to the present invention having any one of the above characteristics is characterized in that the control signal output means multiplexes the first control signal into an optical signal and outputs the multiplexed signal to the optical transmitter. .

  The optical transmission system according to the present invention having any one of the above characteristics is characterized in that the current control signal is defined based on a threshold current value that defines a minimum current for the light emitting element to output the optical signal. And bias current information for setting the value of the modulation current information for setting the value of the modulation current for modulating the optical signal of the light emitting element, the control means of the optical transmission device, Bias current index calculation processing for setting, as a bias current index, the modulation current value or the equivalent value at the output timing of the first control signal when the bias current information is set to 0 and the modulation current information is changed in the increasing direction. The bias current information is set based on the bias current index, and the output timing of the first control signal when the modulation current information is changed in the increasing direction. Modulation current index calculation processing for obtaining the modulation current value or its equivalent value as a modulation current index, and the bias current index, the modulation current index, and the temperature information based on the bias current and the modulation current. A seventh characteristic is that a current control signal generation process for obtaining a value and generating the current control signal is executed.

  To achieve the above object, an optical transmission apparatus according to the present invention generates a first control signal including a light emitting element that generates an optical signal and signal intensity information that receives the optical signal and indicates the signal intensity of the optical signal. Signal intensity information acquisition means for receiving the first control signal from the optical receiver, and temperature detection means for detecting a temperature of the light emitting element and generating a second control signal including temperature information indicating the temperature of the light emitting element Driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal, the signal intensity information of the first control signal, and the temperature information of the second control signal. And a control means for generating the current control signal.

  In order to achieve the above object, an optical receiving apparatus according to the present invention receives an optical signal output from the optical transmitting apparatus having the above characteristics and converts it into an electrical signal, and an optical signal based on the electrical signal. A control signal output for generating a first control signal including signal strength detection means for detecting signal strength and signal strength information indicating the signal strength of the optical signal detected by the signal strength detection means, and outputting the first control signal to the optical transmission device And means.

  To achieve the above object, an optical transmission / reception apparatus according to the present invention includes a light receiving means for converting an externally input optical signal into an electric signal, and a signal intensity detection for detecting the signal intensity of the optical signal based on the electric signal. And an optical receiving unit comprising: a control signal output unit that generates and outputs a first control signal including signal strength information indicating the signal strength of the optical signal detected by the signal strength detection unit; A light emitting element to be generated, a signal intensity information acquisition means for receiving the first control signal input from the outside, a temperature of the light emitting element is detected, and a second control signal including temperature information indicating the temperature of the light emitting element is generated. Temperature detecting means for driving, driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal, the signal intensity information of the first control signal, and the second control signal Of the above Based on the degree information, characterized in that it and a light transmission unit and a control means for generating said current control signal.

  According to the optical transmission system having the above characteristics, in data communication based on the optical transmission method, the optical receiving apparatus outputs signal intensity information indicating the signal intensity detected by the signal intensity detecting means to the optical transmitting apparatus, and the optical transmitting apparatus However, since the light emitting element is controlled based on the signal intensity information, in the optical transmission device, the degradation of the transmission quality in the transmission path from the optical transmission device to the optical reception device is considered. It becomes possible to adjust the signal intensity of the light emitting element. As a result, the transmission quality of the optical signal received by the optical receiving device can be improved by the response on the optical transmitting device side.

  Further, in the optical transmission system having the above characteristics, it is not necessary for the optical transmission device to install other devices than the conventional temperature detection means, and the optical reception device installs other devices other than the conventional signal intensity detection means. Therefore, the number of parts is not significantly increased, and the downsizing of the apparatus is not greatly hindered. Therefore, the optical transmission system having the above characteristics is particularly useful for devices that perform data communication using a relatively short-distance optical transmission method, such as data communication within the same device, in video devices such as mobile phones, personal computers, and televisions. is there.

  According to the optical transmission / reception device having the above characteristics, in data communication by the optical transmission method, the optical reception unit outputs signal strength information indicating the signal strength detected by the signal strength detection unit to another external optical transmission / reception device, Since the optical transmission unit is configured to control the light emitting element based on the signal intensity information output from the external optical transmission / reception device, the device of the present invention can appropriately cope with the deterioration of the transmission quality in the transmission path. become. As a result, the same effect as the optical transmission system having the above characteristics can be expected, and the transmission quality of the optical signal received by the optical receiving apparatus can be improved.

  Embodiments of an optical transmission system according to the present invention (hereinafter, abbreviated as “the present system” as appropriate), an optical transmission device, an optical reception device, and an optical transmission / reception device will be described below with reference to the drawings.

<First Embodiment>
1st Embodiment of this invention system is described based on FIGS.

  First, the configuration of the system of the present invention will be described with reference to FIGS. Here, FIG. 1 shows a schematic configuration example of the inventive system 1 of the present embodiment.

  As shown in FIG. 1, the system 1 of the present invention generates an optical signal and outputs the optical signal via an optical transmission path 31, and the optical signal output from the optical transmission apparatus 10 And an optical receiving device 20 that accepts the data via the receiver. In this embodiment, it is assumed that the system 1 of the present invention is built inside a mobile phone as an example of a small terminal device, and the optical receiver 20 and the optical transmitter 10 are different semiconductors. Description will be made assuming that the semiconductor chip built in the chip and provided with the optical receiver 20 and the semiconductor chip provided with the optical transmitter 10 are installed on the same substrate.

  The optical receiver 20 includes a light receiving element 21 (corresponding to a light receiving means) that converts an optical signal into an electrical signal, a TIA circuit 22 that converts a current signal output from the light receiving element 21 into a voltage signal, and a TIA circuit 22 An AMP circuit 23 that amplifies the output signal, an AMP circuit 24 that amplifies the output signal from the AMP circuit 23 and outputs it to the outside (another circuit in the same semiconductor chip), and an optical signal based on the output signal from the AMP circuit 23 A signal strength detection unit 25 that detects the signal strength of the signal, and a reception-side APC unit 26 that generates and outputs a first control signal including signal strength information indicating the signal strength of the optical signal detected by the signal strength detection unit 25 (control) Including signal output means). In the present embodiment, a photodiode is described as the light receiving element 21, but the present invention is not limited to this.

In the present embodiment, the signal strength detection means 25 determines the strength of the voltage level V _PDIO of the electrical signal output from the AMP circuit 23 and indicates a predetermined signal strength _equal to or higher than the signal strength of the optical signal that can be received by the light receiving element 21. A comparison circuit for comparing with the value is provided.

Here, FIG. 2 shows a schematic configuration example of the signal strength detection means 25 of the optical receiver 20, and FIG. 3 shows the voltage level V of the voltage signal output from the AMP circuit 23 in the signal strength detection means 25. It shows a signal waveform of the signal _{S DET} indicating the detection result of the signal intensity for _PDIO. As shown in FIG. 2, the signal strength detection means 25 receives a reference signal R _Level for setting a strength determination value V _Level from a receiving-side APC unit 26 described later, and performs strength determination by digital-analog conversion of the reference signal R _Level. the DAC circuit 251 for outputting a value _{V level,} is configured to include a comparator 252 for comparing the voltage level _{V PDIO} and intensity determination value _{V level} that indicates the signal intensity of the optical signal (corresponding to the comparison circuit). The comparator 252, as shown in FIG. 3, and outputs a positive pulse signal _{S DET} having a pulse width corresponding to a period in which the voltage level _{V PDIO} showing signal intensity of the optical signal exceeds the intensity determination value _{V Level.}

Recipient APC unit 26, as shown in FIG. 1, accepts a pulse signal _{S DET} to the voltage level _{V PDIO} showing signal intensity of the optical signal is output if it exceeds an intensity determination value _{V Level,} the pulse signal _{S DET} The counter 261 for counting the number of outputs is provided. Furthermore, the receiving APC unit 26, when the value of the counter 261 exceeds the first determination value predetermined, and is configured to output a first control signal C _1.

Note that the first determination value is appropriately set according to the intensity determination value V _Level or the like. Since the intensity determination value V _Level is set to be equal to or higher than the signal intensity of the optical signal that can be received by the light receiving element 21, it is appropriately set according to the semiconductor process, the frequency of the optical signal, and the like. Incidentally, by making the configuration for counting the number of output times of the pulse signal S _DET, especially when the difference between the peak value of the voltage level V _PDIO showing signal intensity of the optical signal and the intensity determination value V _Level is small, the influence of noise Can be reduced.

As shown in FIG. 1, the optical transmitter 10 includes a light emitting element 11 that generates an optical signal, a signal intensity information acquisition unit that receives a first control signal C ₁ from the optical receiver 20 that receives the optical signal, and a light emitting element. 11 for detecting a temperature of the light emitting element 11 and generating a second control signal including temperature information indicating the temperature of the light emitting element 11, and a predetermined current control signal (in this embodiment, bias current I _BIAS , modulation current I based on _MOD), a driver 14 for controlling the intensity of the optical signal emitting element 11 current control to (corresponding to the drive means), the temperature information R _TEMP signal strength information of the first control signal C ₁ and the second control signal And a control means for generating a current control signal. In the present embodiment, the transmission side APC unit 12 and the driver control unit 15 are configured to function as a signal strength information acquisition unit and a control unit.

  In the present embodiment, the light-emitting element 11 will be described assuming a VCSEL (Vertical Cavity Surface Emitting Laser) 11. In this embodiment, the VCSEL 11 is assumed, but an LED (Light Emitting Diode), an LD (Laser Diode), or another light emitting element 11 may be used.

Here, FIG. 4 shows the temperature dependence characteristics of the threshold current I _TH that defines the minimum current for the VCSEL 11 to output an optical signal, and FIG. 5 shows the drive currents I _VCSEL and _VCSEL 11 supplied to the _VCSEL 11. The correlation of the output value _PVCSEL of an optical signal is shown. As can be seen from FIG. 4, the threshold current I _TH has a V-shaped temperature characteristic with the lower limit being around room temperature (about 27 degrees Celsius). 5A shows the IP conversion characteristics of the _{VCSEL 11} , FIG. 5B shows an example of the drive current I _VCSEL supplied to the _{VCSEL 11} , and FIG. 5C shows the drive current shown in FIG. 5B. The output value P _VCSEL of the optical signal corresponding to I _VCSEL is shown. As shown in FIG. 5, when the drive current I _VCSEL is larger than the threshold current I _TH , the optical signal can be modulated.

The driver 14 receives a bias current I _BIAS and a modulation current I _MOD that modulates an optical signal from a driver control unit 15 described later, generates a drive current I _VCSEL to be supplied to the _{VCSEL 11} , and performs current control on the _VCSEL 11. Here, FIG. 6 shows a schematic circuit configuration example of the driver 14, and FIG. 7 shows a drive current I _VCSEL supplied to the _{VCSEL 11} (total value of the bias current I _BIAS and the modulation current I _MOD ). And the output value P _VCSEL of the optical signal of the _{VCSEL 11} is shown.

More specifically, as shown in FIG. 6, the driver 14 includes two current mirror circuits, and constantly supplies a current corresponding to the bias current I _BIAS to the VCSEL 11 and a signal indicating transmission data. based on the voltage level of V _DATA, switch the supply to VCSEL11 current corresponding to the modulation current _{I MOD} (on state) and supply stop (oFF state). By modulating the optical signal in this way, the _{VCSEL 11} outputs an optical signal having an intensity proportional to the drive current I _VCSEL (the total value of the bias current I _BIAS and the modulation current I _MOD ). The bias current I _BIAS is set according to the threshold current I _TH .

In the present embodiment, the drive current I _VCSEL supplied to the _{VCSEL 11} is controlled by being divided into the bias current I _BIAS and the modulation current I _MOD . This is because, as shown in FIG. 5, if, when the bias current _{I BIAS} is set to 0, it is necessary to a value of the modulation current _{I MOD} to the value of the drive current _{I VCSEL,} corresponding variation width of the modulation current _{I MOD} growing. In this case, a nonlinear phenomenon occurs in which the pulse width itself is modulated during the time until the modulation current I _MOD exceeds the threshold current I _TH , which becomes a factor of deteriorating the BER (bit error rate) on the receiving side. . Accordingly, the bias current I _BIAS is set in consideration of the threshold current I _TH and the response speed required for the light emitting element 11, and is constantly supplied to the VCSEL 11, thereby preventing BER deterioration and reducing power consumption. Is possible.

The temperature detection unit 13 includes a temperature sensing element that observes the temperature around the VCSEL 11 and outputs temperature information R _TEMP indicating the temperature detected by the temperature sensing element to the driver control unit 15 described later. . 8A shows the IP conversion characteristics for each temperature of the VCSEL 11 (low temperature, room temperature, and high temperature), and FIG. 8B shows the IP conversion coefficient η of the VCSEL 11 (in FIG. 8A). FIG. 8C shows the temperature-dependent characteristics of the approximate expression of the IP conversion characteristics, and FIG. 8C shows the temperature-dependent characteristics of the threshold current _ITH . As can be seen from FIG. 8A, the slope of the IP conversion characteristics of the VCSEL 11 decreases as the temperature increases. That is, as shown in FIG. 8B, the IP conversion coefficient η of the VCSEL 11 decreases as the temperature increases.

The transmission-side APC unit 12 receives the first control signal C ₁ indicating the signal strength information from the optical receiver 20, and bias current information for setting the value of the bias current I _BIAS based on the first control signal C _1. and R _BIAS, generates a modulation current information _{R MOD} for setting the value of the modulation current _{I MOD.}

The driver control means 15 receives the bias current information R _BIAS and the modulation current information R _MOD from the transmission side APC unit 12 and the temperature information R _TEMP from the temperature detection means 13 respectively, and uses the bias current I _BIAS and the current control signal as current control signals. A modulation current I _MOD is generated. Specifically, the bias current I _BIAS is obtained by adding the temperature compensation amount for the temperature dependence characteristic of the threshold current I _TH to the bias current information R _BIAS . The temperature compensation amount is set based on the slope of the approximate expression of the temperature dependence characteristic of the threshold current I _TH shown in FIG. In FIG. 4, the threshold current I _TH has a substantially V-shaped temperature-dependent characteristic with the room temperature 27 [degrees] as the lower limit, and for simplicity, the case where the temperature is 27 [degrees] or less and 27 [degrees]. Degree] The slope of the approximate expression is calculated in two cases. As shown in FIG. 4, the slope of the approximate expression of the temperature-dependent characteristic of the threshold current I _TH is 0.0096≈0.01 when the room temperature is 27 [degrees] or more, and −0.0105≈when the slope is lower than the room temperature 27 [degrees]. -0.01. From the above, the bias current I _BIAS can be obtained by the first-order approximation equation shown in the following equations 1 and 2.

[Equation 1]
I _BIAS = 0.01 (273 + R _TEMP −300) + R _BIAS (R _TEMP ≧ 27)

[Equation 2]
I _BIAS = −0.01 (273 + R _TEMP −300) + R _BIAS (R _TEMP <27)

The temperature information R _TEMP is a Celsius temperature. Further, the modulation current I _MOD is obtained from the following equation 3 based on FIG.

[Equation 3]
I _MOD = 0.02 (273 + R _TEMP −300) + R _MOD

As shown in FIG. 8, since the IP conversion coefficient η (conversion efficiency) of the VCSEL 11 decreases as the temperature rises, the temperature-dependent characteristic is compensated by increasing the modulation current I _MOD with a temperature coefficient with a slope of 0.02. is doing.

The driver control means 15 of the system 1 according to the present invention obtains the bias current I _BIAS and the modulation current I _MOD by using Equations 1 to 3 in consideration of both transmission quality degradation compensation and temperature compensation in the transmission path, and the current of the VCSEL 11 Take control. Thus, the inventive system 1 can be constructed using the control algorithm of the conventional optical transmission system only by changing the calculation formulas of the bias current I _BIAS and the modulation current I _MOD in the conventional optical transmission system. become. Therefore, complicated control is required when the transmission quality deterioration compensation and the temperature compensation are separately performed in the transmission path. In the system 1 of the present invention, the calculation formulas of the bias current I _BIAS and the modulation current I _MOD are changed. Therefore, it is possible to realize both transmission quality deterioration compensation and temperature compensation in the transmission path without requiring complicated control.

In this embodiment, for the sake of simplicity, Equations 1 to 3 for _obtaining the bias current I _BIAS and the modulation current I _MOD are first-order approximations. However, the present invention is not limited to this, and the second-order approximation is more precise. You may comprise so that it may obtain | require by the above approximate expression.

Hereinafter, a setting method of the bias current I _BIAS and the modulation current I _{MOD in} the transmission side APC unit 12 and the driver control means 15 will be described with reference to FIG.

First, as a pre-process for inputting the clock signal as the transmission signal V _DATA to the optical transmission apparatus 10 and obtaining the bias current information R _BIAS , the transmission side APC unit 12 of the optical transmission apparatus 10 uses the APC communication path 32. Then, an initialization signal for initializing the counter 261 is output to the reception side APC unit 26 of the optical receiver 20. Subsequently, the transmission side APC unit 12 sets the bias current information R _BIAS and the modulation current information R _MOD to 0. Further, in order to obtain the bias current information R _BIAS , the transmission side APC unit 12 of the optical transmission device 10 changes the modulation current information R _MOD in the increasing direction, and the modulation current information R at the output timing of the first control signal C _1. The value of _MOD (equivalent value of modulation current I _MOD ) is obtained as a bias current index (corresponding to bias current index calculation processing).

More specifically, the transmitting-side APC unit 12 sets the bias current information R _BIAS and the modulation current information R _MOD to 0 at time T0, and increases the modulation current information R _MOD by 1 every fixed period. At this time, as the modulation current information R _MOD is increased by one, as shown in FIG. 3, the amplitude of the signal strength V _PDIO of the optical signal received by the signal strength detection means 25 of the optical receiver 20 gradually increases. The amplitude of the signal strength _{V PDIO} of the optical signal detected by the optical receiver 20 is increased, the peak value becomes to exceed the intensity determination value _{V Level,} the pulse signal _{S DET} from the signal strength detection means 25 is output. Recipient APC unit 26, the count value of the pulse signal _{S DET} exceeds a first determination value predetermined, and outputs the control signal _{C 1.} In the present embodiment, as shown in FIG. 9, at time T1, the control signal C ₁ is output from the optical receiver 20. When the control signal C ₁ is output from the optical receiver 20, the transmitting APC unit 12 of the optical transmitter 10 sets the modulation current information R _MOD value “0x0a” at this time as a bias current index. Thereby, the bias current index can be appropriately obtained based on the threshold current _ITH .

Subsequently, as pre-processing for obtaining the modulation current information R _MOD , as shown in FIG. 9, the transmission side APC unit 12 of the optical transmission apparatus 10 receives the reception side of the optical reception apparatus 20 via the APC communication path 32. An initialization signal for initializing the counter 261 is output to the APC unit 26. Subsequently, the transmission side APC unit 12 of the optical transmission apparatus 10 sets the bias current information R _BIAS based on the bias current index, and sets the modulation current information R _MOD to 0. Further, in order to obtain the modulation current information R _MOD , the transmission side APC unit 12 of the optical transmission apparatus 10 changes the modulation current information R _MOD in the increasing direction, and the modulation current information R at the output timing of the first control signal C _{1. The MOD} value (equivalent value of the modulation current I _MOD ) is obtained as a modulation current index (corresponding to the modulation current index calculation process).

More specifically, as shown in FIG. 9, the transmission side APC unit 12 of the optical transmission apparatus 10 sets the bias current information R _BIAS to the bias current index 0x0a and sets the modulation current information R _MOD to 0 at time T2. To do. Then, the modulation current information R _MOD is increased by 1 for each fixed period. Accordingly, as described above, when the amplitude of the signal intensity V _PDIO of the optical signal detected by the optical receiver 20 increases and the peak value exceeds the intensity determination value V _Level , the signal of the optical receiver 20 A pulse signal _SDET is output from the intensity detector 25. Recipient APC unit of the optical receiver 20 26, the count value of the pulse signal _{S DET} exceeds a first determination value predetermined, and outputs the control signal _{C 1.} In the present embodiment, as shown in FIG. 9, at time T3, the control signal C ₁ is output from the optical receiver 20. Sender APC unit 12 of the optical transmitter 10 at time T3, the control signal _{C 1} from the optical receiver 20 is output, the value "0x1d" of the modulation current information _{R MOD} at this time the modulation current index . Thereby, the modulation current information R _MOD that sufficiently satisfies the BER can be obtained.

Subsequently, the transmission-side APC unit 12 obtains values of the bias current I _BIAS and the modulation current I _MOD based on the bias current index, the modulation current index, and the temperature information R _TEMP and generates a current control signal (current control signal). Signal generation processing). Here, the value of the bias current information R _BIAS is set to “0x0a”, and the value of the modulation current information R _MOD is set to “0x1d”, thereby setting the values of the bias current I _BIAS and the modulation current I _MOD .

<Another embodiment>
<1> In the above embodiment, the system 1 of the present invention has been described on the assumption that the system 1 is mounted on a mobile phone. However, the present invention is not limited to this. It can also be installed in other devices such as small terminal devices such as personal computers and televisions. Moreover, although the said embodiment demonstrated the case where the one optical receiver 20 was installed with respect to the optical transmitter 10, the optical transmitter 10 is based on the some optical receiver 20 and an optical transmission system. Data communication may be configured.

  Further, in the above-described embodiment, the case where the optical receiver 20 and the optical transmitter 10 constituting the system 1 of the present invention are constructed in different semiconductor chips, respectively, as shown in FIG. Both the optical receiver 20 (optical receiver 20 ′) and the optical transmitter 10 (optical transmitter 10 ′) may be built in the chip. The configuration of the optical receiver 20 'is the same as that of the optical receiver 20 in the above embodiment, and the configuration of the optical transmitter 10' is the same as that of the optical transmitter 10 in the above embodiment.

<2> In the above embodiment, the optical receiving apparatus 20, but the first control signal C ₁ is configured to output to the optical transmission apparatus 10 by the APC communication, not limited to this. For example, as shown in FIG. 11, in the case of an optical transceiver 1A in which an optical receiver 20 ′ (optical receiver 20) and an optical transmitter 10 ′ (optical transmitter 10) are constructed in the same semiconductor chip. , recipient APC unit 26 of the optical transceiver apparatus 1A, the optical transmission section 10 of the optical transceiver 1A outputs a first control signal C _1, the transmission unit 10 of the optical transceiver 1A is a control signal C1 to the light signal multiplexing And may be configured to output to the optical transceiver 1B. If comprised in this way, it can be anticipated that an apparatus structure will be restrained small. Also, other communication means provided separately may be used.

<3> In the above embodiment, the value of the counter 261 which defines a first output timing of the control signal C ₁ (the first determination value), may be re-settable configuration by an external input. Specifically, for example, as shown in FIG. 12, the optical receiving device 20 is provided with an external input means 27 for receiving the first determination value or its equivalent value inputted externally, and the receiving side APC unit 26 is connected to the external input device. The first determination value is reset based on the first determination value or its equivalent value.

<4> In the above embodiment, the case has been described in which the reception-side APC unit 26 of the optical receiver 20 is configured to count the number of times of output of the signal _SDET . However, the present invention is not limited to this.

For example, the reception-side APC unit 26 may be configured using an integration circuit that integrates the voltage level of the electrical signal instead of the counter 261. In this case, the recipient APC unit 26, when the value of the integration circuit exceeds a predetermined second determination value, configured to output a first control signal C _1. Note that when the receiving side APC unit 26 is configured using an integrating circuit, the voltage level (peak value) of the voltage signal _{VIN and} the voltage of the reference signal V _Level are particularly the same as when configured with the counter 261. When the level difference is small, the influence of noise can be reduced.

  In this case, an integration circuit value (second determination value) that defines the output timing of the second control signal may be configured to be reset by an external input. Specifically, for example, the external input unit 27 of the optical receiver 20 shown in FIG. 12 is configured to receive the second determination value or its equivalent value input from the outside, and the receiving side APC unit 26 is connected to the external input unit. The second determination value is reset based on the second determination value or its equivalent value.

Schematic block diagram showing a schematic configuration example of an optical transmission system according to the present invention 1 is a schematic block diagram showing a schematic configuration example of signal intensity detection means of an optical receiving device constituting an optical transmission system according to the present invention. Schematic waveform diagram for explaining an example of the operation of the signal intensity detecting means of the optical receiver constituting the optical transmission system according to the present invention. Schematic partial waveform diagram showing temperature characteristics of a light emitting element of an optical transmission apparatus constituting an optical transmission system according to the present invention Schematic partial waveform diagram showing current characteristics of light-emitting elements of an optical transmission apparatus constituting an optical transmission system according to the present invention 1 is a schematic block diagram showing a schematic configuration example of a driver of an optical transmission device constituting an optical transmission system according to the present invention. Schematic partial waveform diagram showing current characteristics of light-emitting elements of an optical transmission apparatus constituting an optical transmission system according to the present invention Schematic partial waveform diagram showing temperature characteristics of a light emitting element of an optical transmission apparatus constituting an optical transmission system according to the present invention Schematic partial waveform diagram showing the initial setting operation of the optical transmission system according to the present invention Schematic block diagram showing a schematic configuration example of another embodiment of the optical transmission system according to the present invention Schematic block diagram showing a schematic configuration example of another embodiment of the optical transmission system according to the present invention Schematic block diagram showing a schematic configuration example of another embodiment of the optical transmission system according to the present invention Schematic block diagram showing a schematic configuration example of a conventional optical transmission system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical transmission system 1A concerning this invention Optical transmission / reception apparatus 1B concerning this invention Optical transmission / reception apparatus 10 concerning this invention Optical transmission apparatus 10 'concerning this invention Optical transmission part 11 Light emitting element 12 Transmission side APC unit 13 Temperature detection means 14 Driver (drive means)
15 Driver control means 20 Optical receiver 20 'according to the present invention Optical receiver 21 Light receiving element (light receiving means)
22 TIA circuit 23 AMP circuit 24 AMP circuit 25 Signal strength detection means 26 Reception side APC unit 27 External input means 31 Optical transmission path 31 ′ Optical transmission path 32 APC communication path 32 ′ APC communication path 100 Base station side optical transceiver 110 Light Transmitting device 111 Light emitting element 112 Light receiving element for signal intensity detection 113 APC control means 114 Driver 115 Driver control means 120 Optical receiving apparatus 121 Light receiving element 122 TIA circuit 123 AMP circuit 200 Terminal side optical transmission / reception apparatus 210 Optical receiving apparatus 211 Light receiving element 212 TIA Circuit 213 AMP circuit 214 AMP circuit 215 Distance estimation means 220 Optical transmission device 221 Light emitting element 222 Driver 223 APC control means 224 Driver control means 251 DAC circuit 252 Comparator (comparison circuit)
261 counter 301 downstream 302 upstream

Claims (10)

Light receiving means for converting an optical signal into an electric signal, signal intensity detecting means for detecting the signal intensity of the optical signal based on the electric signal, and a signal indicating the signal intensity of the optical signal detected by the signal intensity detecting means Control signal output means for generating and outputting a first control signal including intensity information, or one or a plurality of optical receivers,
A light-emitting element that generates the optical signal; a signal intensity information acquisition unit that receives the first control signal from the optical receiver that receives the optical signal; and a temperature of the light-emitting element that detects the temperature of the light-emitting element. Temperature detecting means for generating a second control signal including temperature information indicating, driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal, and the first control signal An optical transmission system comprising: a control means for generating the current control signal based on the signal intensity information and the temperature information of the second control signal. The signal intensity detection means comprises a comparison circuit for comparing the voltage level of the electrical signal with an intensity judgment value indicating a predetermined signal intensity equal to or higher than the signal intensity of the optical signal receivable by the light receiving means;
The control signal output means includes a counter that is added when it is detected in the comparison circuit that the voltage level continuously exceeds the intensity determination value for a predetermined period or longer, and the counter value is a predetermined first value. The optical transmission system according to claim 1, wherein the first control signal is output when a determination value is exceeded. The optical receiver includes an external input unit that receives the first determination value or its equivalent value input from the outside,
The optical transmission system according to claim 2, wherein the control signal output unit resets the first determination value based on the first determination value or an equivalent value input from the outside. The signal strength detecting means comprises an integrating circuit for integrating the voltage level of the electrical signal;
2. The optical transmission system according to claim 1, wherein the control signal output unit outputs the first control signal when a value of the integration circuit exceeds a predetermined second determination value. 3. The optical receiving device includes external input means for receiving the second determination value or its equivalent value input from the outside,
5. The optical transmission system according to claim 4, wherein the control signal output unit resets the second determination value based on the second determination value or an equivalent value input from the outside. 6.   The optical transmission system according to claim 1, wherein the control signal output unit multiplexes the first control signal with an optical signal and outputs the multiplexed signal to the optical transmission device. The current control signal includes bias current information for setting a bias current value defined based on a threshold current value defining a minimum current for the light emitting element to output the optical signal; and the light emitting element. Including modulation current information for setting the value of the modulation current for modulating the optical signal of
The control means of the optical transmitter is
Bias current index calculation for determining, as a bias current index, the modulation current value or the equivalent value at the output timing of the first control signal when the bias current information is set to 0 and the modulation current information is changed in the increasing direction. Processing,
The bias current information is set based on the bias current index, and the modulation current value or the equivalent value at the output timing of the first control signal when the modulation current information is changed in the increasing direction is used as the modulation current index. A modulation current index calculation process to be obtained;
Performing a current control signal generation process for determining the values of the bias current and the modulation current based on the bias current index, the modulation current index, and the temperature information, and generating the current control signal. The optical transmission system according to any one of claims 1 to 6, characterized in that A light emitting element for generating an optical signal;
Signal intensity information acquisition means for receiving the first control signal from an optical receiver that receives the optical signal and generates a first control signal including signal intensity information indicating the signal intensity of the optical signal;
Temperature detecting means for detecting a temperature of the light emitting element and generating a second control signal including temperature information indicating the temperature of the light emitting element;
Driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal;
An optical transmission apparatus comprising: control means for generating the current control signal based on the signal strength information of the first control signal and the temperature information of the second control signal. A light receiving means for receiving an optical signal output from the optical transmission device according to claim 8 and converting it into an electrical signal;
Signal intensity detection means for detecting the signal intensity of the optical signal based on the electrical signal;
Control signal output means for generating a first control signal including signal intensity information indicating the signal intensity of the optical signal detected by the signal intensity detection means, and outputting the first control signal to the optical transmission device. Receiver device. A light receiving means for converting an externally input optical signal into an electrical signal;
Signal intensity detection means for detecting the signal intensity of the optical signal based on the electrical signal;
A control signal output unit that generates and outputs a first control signal including signal strength information indicating the signal strength of the optical signal detected by the signal strength detection unit;
A light emitting element for generating an optical signal;
Signal strength information acquisition means for receiving the first control signal inputted externally;
Temperature detecting means for detecting a temperature of the light emitting element and generating a second control signal including temperature information indicating the temperature of the light emitting element;
Driving means for controlling the intensity of the optical signal by controlling the current of the light emitting element based on a predetermined current control signal;
An optical transmitter comprising: control means for generating the current control signal based on the signal strength information of the first control signal and the temperature information of the second control signal. Optical transceiver.

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