JP2007288700A - Optical modulation apparatus, repeating system using same, and network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical modulation apparatus capable of simultaneously suppressing second-order nonlinear distortion and third-order nonlinear distortion. <P>SOLUTION: An optical modulation apparatus 10 comprises a laser light source 1, an optical modulator 2, and a control unit 3. The control unit 3 controls the laser light source 1 so as to generate a laser beam LB1 having a wavelength λ for suppressing nonlinear distortion (= second-order distortion and third-order distortion) when converting a voltage V into a laser beam LB2 (optical signal). The laser light source 1 generates the laser beam LB1 having the wavelength λ in accordance with control from the control unit 3 and guides the generated laser beam LB1 to the optical modulator 2. The optical modulator 2 converts the voltage V into the laser beam LB2 by converting intensity of the laser beam LB1 into transmission intensity corresponding to the voltage V. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical modulation device, a relay system and a network system using the same, and more particularly to an optical modulation device capable of suppressing nonlinear distortion, a relay system and a network system using the same.

  In recent years, a service system related to the fusion of broadcasting and communication has attracted attention, and research on a software optical fiber radio network (SDNW: Software Defined Radio-on-Fiber Network) as a base network for realizing a fusion system of broadcasting and communication. It is done.

  In the SDNW, a RoF (Radio-on-Fiber) network is a link between a user terminal (such as a mobile phone and a PDA (Personal Digital Assistant)), an Intelligent Transport System (ITS), and the Internet. Fulfill the function of building.

  The RoF network collects RF signals whose intensity changes in a complex manner, such as UHF (Ultra High Frequency) digital broadcasting, 2 GHz band 3G mobile phone, and 5 GHz band wireless LAN (IEEE802.11a, IEEE802.11n). Therefore, it is necessary to perform optical modulation directly, so that it requires an optical conversion technique for radio waves having a very high dynamic range, that is, low distortion / low noise.

2. Description of the Related Art Conventionally, an electro-absorption modulator (EAM) is known as a device that converts an electrical signal into an optical signal (Non-patent Document 1). This electroabsorption optical modulator outputs a transmission intensity of incident light set to a transmission intensity proportional to the applied voltage, and is generally operated at a bias voltage that minimizes distortion.
Young-Shik Kang, Jiyoun Lim, Sung-Bok Kim, Jeha Kim, “Improvement of linearity in EAM by composites QWs”, International Topic Met.

  However, in a conventional electroabsorption optical modulator, it is difficult to simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion that cause distortion during multi-octave transmission.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide an optical modulation device capable of simultaneously suppressing second-order nonlinear distortion and third-order nonlinear distortion.

  Another object of the present invention is to provide a relay system including an optical modulation device that can simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion.

  Furthermore, another object of the present invention is to provide a network system including an optical modulation device that can simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion.

  According to the invention, the light modulation device includes the light modulator and the light source. The optical modulator sets the transmission intensity of incident light to a transmission intensity proportional to the applied voltage and outputs the transmission intensity. The light source generates laser light having a wavelength that suppresses nonlinear distortion in the relationship between the output of the optical modulator and the applied voltage, and guides the generated laser light to the optical modulator as incident light.

  Preferably, the light modulation device further includes control means. The control means detects nonlinear distortion based on the output of the optical modulator, detects a wavelength for suppressing the detected nonlinear distortion, and controls the light source to emit laser light having the detected wavelength. To do. The light source generates laser light having a wavelength detected by the control means in accordance with control from the control means and guides it to the optical modulator.

  Preferably, the control means holds a table indicating the relationship between the shift amount of the wavelength of the laser beam to be shifted to suppress the nonlinear distortion and the applied voltage. When the nonlinear distortion is detected, the control means refers to the table. A shift amount is detected, and a wavelength for suppressing nonlinear distortion is detected based on the detected shift amount.

  According to the invention, the relay system includes a receiver, a light modulation device, an optical fiber transmission line, and a transmitter. The receiver receives a radio signal, converts the received radio signal into an electric signal composed of a voltage, and outputs the electric signal. The optical modulation device converts an electrical signal from the receiver into an optical signal and outputs the optical signal. The optical fiber transmission line transmits the optical signal output from the light modulation device. The transmitter converts the optical signal transmitted through the optical fiber transmission line into an electric signal and radiates the converted electric signal as a radio signal. The light modulation device includes a light modulator and a light source. The optical modulator sets the transmission intensity of incident light to a transmission intensity proportional to the voltage constituting the electric signal and outputs the transmission intensity to the optical fiber transmission line. The light source generates laser light having a predetermined wavelength that suppresses nonlinear distortion in the relationship between the output of the optical modulator and the electrical signal, and guides the generated laser light to the optical modulator as incident light.

  Furthermore, according to this invention, the relay system includes first and second transceivers, first and second transceiver modules, and first and second optical fiber transmission lines. The first transceiver receives the first radio signal from the radio communication space, converts the received first radio signal into a first electric signal composed of the first voltage, and outputs the first electric signal. Is converted into a first wireless signal and transmitted to the wireless communication space. The first transceiver module converts the first electrical signal from the first transceiver to the first optical signal and outputs the first optical signal, and converts the second optical signal to the second electrical signal to convert the first electrical signal into the first electrical signal. Output to the transceiver. The first optical fiber transmission line transmits the first optical signal output from the first optical modulation device. The second transmitting / receiving module converts the first optical signal transmitted by the first optical fiber transmission line into a third electric signal, outputs the converted third electric signal, and outputs the second voltage. The fourth electric signal consisting of is converted into a second optical signal and output. The second transceiver converts the third electrical signal into a second radio signal and transmits it to the radio communication space, receives the second radio signal from the radio communication space, and receives the received second radio signal. The signal is converted into a fourth electrical signal and output to the second transceiver module. The second optical fiber transmission line transmits the second optical signal output from the second transmission / reception module to the first transmission / reception module. The first transmission / reception module includes a first light modulation device and a first photoelectric converter. The first optical modulation device converts the first electrical signal into a first optical signal and outputs the first optical signal to the first optical fiber transmission line. The first photoelectric converter converts the second optical signal into a second electrical signal. The second transmission / reception module includes a second photoelectric converter and a second light modulation device. The second photoelectric converter converts the first optical signal into a third electrical signal. The second optical modulation device converts the fourth electric signal into a second optical signal. The first light modulation device includes a first light modulator and a first light source. The first optical modulator sets the transmission intensity of the first incident light to a transmission intensity proportional to the first voltage constituting the first electric signal, and outputs the transmission intensity to the first optical fiber transmission line. The first light source generates a first laser beam having a first wavelength that suppresses nonlinear distortion in the relationship between the output of the first optical modulator and the first voltage, and the generated first laser The light is guided to the first light modulator as the first incident light. The second light modulation device includes a second light modulator and a second light source. The second optical modulator sets the transmission intensity of the second incident light to a transmission intensity proportional to the second voltage constituting the fourth electric signal and outputs the transmission intensity to the second optical fiber transmission line. The second light source generates a second laser beam having a second wavelength that suppresses nonlinear distortion in the relationship between the output of the second optical modulator and the second voltage, and the generated second laser The light is guided to the second light modulator as second incident light.

  Furthermore, according to the present invention, the network system includes a communication device, a communication device, first and second transmission / reception modules, and an optical fiber transmission line. The communication device transmits / receives a digital signal to / from the communication network, and converts the digital signal received from the communication network into a first analog signal having a first voltage. The communication device communicates with a communication device. The first transmission / reception module converts the first analog signal received from the communication device into an optical signal, outputs the optical signal, receives the optical signal, converts the received optical signal into the first analog signal, and performs communication. Output to the device. The second transmission / reception module receives an optical signal, converts the received optical signal into a second analog signal composed of a second voltage, outputs the second analog signal, and converts the second analog signal into an optical signal. Output to communication equipment. The optical fiber transmission line transmits an optical signal between the first and second transmission / reception modules. The first transmission / reception module includes a first light modulation device and a first photoelectric converter. The first light modulation device converts the first analog signal into an optical signal and outputs the optical signal to the optical fiber transmission line. The first photoelectric converter converts the optical signal into a first analog signal. The second transmission / reception module includes a second photoelectric converter and a second light modulation device. The second photoelectric converter converts the optical signal into a second analog signal. The second light modulation device converts the second analog signal into an optical signal and outputs the optical signal to the optical fiber transmission line. The first light modulation device includes a first light modulator and a first light source. The first optical modulator sets the transmission intensity of the first incident light to a transmission intensity proportional to the first voltage constituting the first analog signal, and outputs the transmission intensity to the optical fiber transmission line. The first light source generates a first laser beam having a first wavelength that suppresses nonlinear distortion in the relationship between the output of the first optical modulator and the first voltage, and the generated first laser The light is guided to the first light modulator as the first incident light. The second light modulation device includes a second light modulator and a second light source. The second optical modulator sets the transmission intensity of the second incident light to a transmission intensity proportional to the second voltage constituting the second analog signal, and outputs the transmission intensity to the optical fiber transmission line. The second light source generates a second laser beam having a second wavelength that suppresses nonlinear distortion in the relationship between the output of the second optical modulator and the second voltage, and the generated second laser The light is guided to the second light modulator as second incident light.

  Preferably, the communication device, the communication device, the first and second transmission / reception modules, and the optical fiber transmission line are arranged in the house.

  Preferably, the communication device includes at least one of a digital home appliance and an AV device.

  Preferably, the communication device is a wireless device that performs wireless communication with the second transmission / reception module.

  Preferably, the communication device includes at least one of a wireless device that performs wireless communication with the second transmission / reception module, a digital home appliance, and an AV device.

  An optical modulator according to the present invention includes an optical modulator that sets the transmission intensity of incident light to a transmission intensity corresponding to an applied voltage and outputs the non-linear distortion (second-order distortion and third-order distortion when the voltage is converted into laser light. And a light source for generating laser light having a predetermined wavelength for suppressing distortion and guiding the generated laser light as incident light to an optical modulator.

  Therefore, according to the present invention, second-order distortion and third-order distortion can be suppressed simultaneously.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic block diagram showing a configuration of a light modulation device according to an embodiment of the present invention. Referring to FIG. 1, an optical modulation device 10 according to an embodiment of the present invention includes a laser light source 1, an optical modulator 2, and a control unit 3.

  The laser light source 1 is a laser whose wavelength can be switched. Then, the laser light source 1 generates laser light having a wavelength λ in accordance with control from the control unit 3, and guides the generated laser light LB 1 to the optical modulator 2.

  The optical modulator 2 includes an electroabsorption optical modulator (EAM) whose light transmission intensity is proportional to the applied voltage. Then, the optical modulator 2 sets the transmission intensity of the laser beam LB1 from the laser light source 1 to a transmission intensity proportional to the voltage V received from the control unit 3 and outputs the laser beam LB2.

  The control unit 3 performs nonlinear distortion (= second order and 3rd order) in the relationship between the output of the optical modulator 2 (= laser beam LB2) and the voltage V when the voltage V is applied to the optical modulator 2 by a method described later. The wavelength λ for suppressing the next nonlinear distortion) is determined, and the laser light source 1 is controlled so as to generate the laser light LB1 having the determined wavelength λ. That is, the control unit 3 controls the laser light source 1 and the optical modulator 2 so as to suppress nonlinear distortion in the output of the optical modulator 2 by the voltage V and the wavelength λ.

  Next, a method for suppressing nonlinear distortion in the output of the optical modulator 2 will be described. FIG. 2 is a diagram showing the relationship between the light output and the bias voltage in the electroabsorption optical modulator used in the experiment.

  In FIG. 2, the vertical axis represents the light output, and the horizontal axis represents the bias voltage. A curve k1 indicates the relationship between the optical output of the electroabsorption optical modulator EAM1 and the bias voltage, and a curve k2 indicates the relationship between the optical output of the electroabsorption optical modulator EAM2 and the bias voltage.

  In each of the electroabsorption optical modulators EAM1 and EAM2, the optical output decreases exponentially as the bias voltage applied to the electroabsorption optical modulators EAM1 and EAM2 changes from a positive voltage to a negative voltage. .

  When the optical output characteristics of the electroabsorption optical modulators EAM1 and EAM2 are approximated by an exponential function of the bias voltage V, the following expression is obtained.

In Equation (1), V is a bias voltage, P ₀ is an optical output power when the bias voltage V is 0 V, and t _{0 to} t ₄ are constants.

  As described above, the optical outputs of the electroabsorption optical modulators EAM1 and EAM2 are approximated by a polynomial using a fourth-order exponent term.

  FIG. 3 is a diagram showing the relationship between the optical output of the electroabsorption optical modulator and the bias voltage when the wavelength is changed. FIG. 4 is a diagram showing the relationship between the light output of the electroabsorption optical modulator and the wavelength when the bias voltage is changed.

  In FIG. 3, the vertical axis represents the light output, and the horizontal axis represents the bias voltage. Curves k3 to k6 show the relationship between the optical output and the bias voltage when the wavelengths are 1545 nm, 1555 nm, 1565 nm, and 1575 nm, respectively.

  In FIG. 4, the vertical axis represents the light output, and the horizontal axis represents the wavelength. Curves k7 to k12 show the optical output and wavelength when the bias voltage V is 0V, -0.2V, -0.4V, -0.6V, -0.8V, and -1.0V, respectively. Show the relationship.

  Referring to FIG. 3, at each wavelength, the optical output decreases exponentially as the bias voltage V changes from a positive voltage to a negative voltage. At one bias voltage, the light output becomes stronger as the wavelength becomes longer.

  When the optical output is measured at 1 nm intervals in the wavelength range of 1560 nm to 1580 nm, it is as shown in FIG. Referring to FIG. 4, at each bias voltage, the optical output increases exponentially as the wavelength increases. When the optical output characteristic in the electroabsorption optical modulator is approximated by an exponential function of the wavelength λ, the following equation is obtained.

In the formula (2), r _{0 to} r ₄ are constants.

  The light output characteristic of the electroabsorption optical modulator is expressed by the equation (1) with respect to the bias voltage V and is expressed by the equation (2) with respect to the wavelength λ. Therefore, the optical output characteristic in the electroabsorption optical modulator is expressed by the following equation with respect to the bias voltage V and the wavelength λ.

In Equation (3), T _{λ = λ1} (V) represents the intensity transmission characteristic with respect to the bias voltage V at the wavelength λ1, and R _{V = V1} (λ) represents the intensity transmission characteristic with respect to the wavelength λ at the bias voltage V1. To express.

  Therefore, the intensity transmission characteristic of the electroabsorption optical modulator with respect to the bias voltage V and the wavelength λ is expressed by the following equation obtained by Taylor expansion of equation (3).

  The bias voltage V and the wavelength λ of the electroabsorption optical modulator can be regarded as independent variables with respect to the intensity transmission characteristics when viewed in a narrow range. The transmission characteristic can be expressed by the sum of the Taylor expansion by each of the bias voltage V and the wavelength λ, as in the following equation.

  The condition that non-linear distortion does not occur is that the optical output of the electroabsorption optical modulator is proportional to the bias voltage V, so that it can be adjusted so that the proportional relationship is established between the wavelength λ and the bias voltage V. Non-linear distortion does not occur.

  When generalized, the nth derivative of Equation (1) is expressed by the following equation.

  Similarly, when generalized, the n-th derivative of Equation (2) is expressed by the following equation.

Constant _t 0 ~t ₄ and the constant _r 0 ~r ₄ of formula (2) of formula (1) in the case of wavelength lambda = 1570 nm and the bias voltage V1 = -0.4 V shown in Table 1.

With constant _t 0 ~t ₄ and the constant _r 0 ~r ₄ shown in Table 1, Equation (3) is expressed by the following equation.

  Therefore, the relationship between the bias voltage V and the wavelength λ can be obtained by the following simultaneous equations.

  K is a constant.

  Since Equation (9) is complicated and difficult to solve, the relationship between the bias voltage V and the wavelength λ having the relationship shown in Equation (9) was obtained by numerical calculation.

  FIG. 5 is a diagram showing the relationship between the wavelength shift and the RF voltage when the relationship between the bias voltage V and the wavelength λ in Equation (9) is obtained by numerical calculation. In FIG. 5, the vertical axis represents the wavelength shift, and the horizontal axis represents the RF voltage.

Curve k13 shows the relationship between the RF shift and the wavelength shift that is numerically calculated so that the terms V ² , V ³ , λ, λ ² , and λ ³ in Equation (9) are eliminated. Indicates. That is, a relationship between the wavelength shift and the RF voltage that are numerically calculated so as to eliminate the second-order distortion and the third-order distortion is shown.

As described above, λ in equation (9) is a variation in wavelength centered on wavelength λ1 = 1570 nm, and V in equation (9) is a variation in voltage centered on voltage V1 = −0.4V. Minutes. Therefore, λ and V, which are numerically calculated so that the terms V ² , V ³ , λ, λ ² , and λ ³ are eliminated, respectively, are the wavelength variation in FIG. Represents the voltage fluctuation.

  Then, when λ (= wavelength variation) and V (= voltage variation) numerically calculated by the above-described method are plotted, a curve k13 shown in FIG. 5 is obtained.

  In the light modulation device 10, the control unit 3 holds a curve k13. And the control part 3 calculates | requires the wavelength shift corresponding to RF voltage applied to the optical modulator 2 with reference to the curve k13, and erase | eliminates a secondary distortion and a tertiary distortion based on the calculated | required wavelength shift. Find the wavelength for

  For example, when the voltage variation (= RF voltage) applied to the optical modulator 2 is 0.2V, the control unit 3 refers to the curve k13 and has a wavelength of 23 nm corresponding to the RF voltage of 0.2V. Find a shift. Since this 23 nm wavelength shift represents a wavelength shift from 1570 nm, the control unit 3 adds 23 nm to 1570 nm and sets the wavelength for eliminating the second and third order distortions to 1593 nm (= 1570 nm + 23 nm). I ask.

  And the control part 3 will control the laser light source 1 so that the laser beam which has the calculated | required wavelength (= 1593nm) will be generated, if the wavelength for erasing a secondary distortion and a tertiary distortion is calculated | required.

  The overall operation of the light modulation device 10 will be described. When the control unit 3 applies a voltage V with an RF voltage of 0.6V centered on V1 = −0.4V to the optical modulator 2, the control unit 3 corresponds to the RF voltage of 0.6V with reference to the curve k13. The 22 nm wavelength shift is obtained, and the obtained wavelength shift (= 23 nm) is added to 1570 nm, and the wavelength for eliminating the second order distortion and the third order distortion is obtained as 1592 nm (= 1570 nm + 22 nm).

  Then, the control unit 3 controls the laser light source 1 so as to generate the laser beam LB1 having the obtained wavelength of 1592 nm, and emits the voltage V (center voltage: −0.4 V, RF voltage: 0.6 V). Output to the modulator 2.

  The laser light source 1 generates laser light LB1 having a wavelength of 1592 nm in accordance with control from the control unit 3, and guides the generated laser light LB1 to the optical modulator 2. The optical modulator 2 receives the voltage V (center voltage: −0.4 V, RF voltage: 0.6 V) from the control unit 3, and receives the laser light LB 1 from the laser light source 1. Then, the optical modulator 2 converts the intensity of the laser beam LB1 into a transmission intensity corresponding to the voltage V (center voltage: −0.4 V, RF voltage: 0.6 V), so that the voltage V (center voltage: − 0.4V, RF voltage: 0.6V) is converted into laser beam LB2, and the converted laser beam LB2 is output.

  In this case, the wavelength of the laser beam LB1 is the second-order distortion and the third-order distortion when the voltage V (center voltage: −0.4 V, RF voltage: 0.6 V) is converted into the laser beam LB2 in the optical modulator 2. Since the optical modulator 2 has a wavelength that suppresses distortion (= 1589 nm), the optical modulator 2 suppresses nonlinear distortion (= second-order distortion and third-order distortion) based on the laser beam LB1, and voltage V (center voltage: -0.4V, RF voltage: 0.6V) is converted into laser beam LB2.

  Thus, the light modulation device 10 is a laser beam having a wavelength λ for suppressing nonlinear distortion (= second-order distortion and third-order distortion) when the voltage V is converted into the laser light LB2 (optical signal). The control unit 3 that controls the laser light source 1 to generate LB1, the laser light source 1 that generates the laser light LB1 having the wavelength λ according to the control from the control unit 3, and the intensity of the laser light LB1 is set to the voltage V (center The voltage V (center voltage: -0.4 V, RF voltage: 0.6 V) is converted into the laser beam LB2 by converting the transmission intensity according to the voltage: -0.4 V and the RF voltage: 0.6 V. And an optical modulator 2.

  Therefore, according to the present invention, the non-linear distortion (= second order distortion and third order distortion) is suppressed, and the voltage V (center voltage: −0.4 V, RF voltage: 0.6 V) is converted into the laser beam LB2. it can.

[Application Example 1]
FIG. 6 is a schematic block diagram showing a configuration of a relay system using the light modulation device according to the embodiment of the present invention. With reference to FIG. 6, the relay system 100 includes an optical modulation device 10, a receiver 20, an optical fiber transmission line 30, a photoelectric converter 40, and a transmitter 50.

  In the relay system 100, the laser light source 1 is connected to the optical modulator 2 by an optical fiber transmission line 4.

  The light modulation device 10 is connected to the photoelectric converter 40 by an optical fiber transmission line 30. The receiver 20 is connected to the light modulator 2 of the light modulation device 10. The photoelectric converter 40 is connected to the optical modulator 2 by the optical fiber transmission line 30 and to the transmitter 40.

  The receiver 20 receives a radio signal RF from the radio communication space, converts the received radio signal RF into an electric signal ES (V) composed of a voltage V, and outputs the electric signal ES (V) to the optical modulator 2 of the optical modulation device 10. In the optical modulation device 10, the control unit 3 detects the voltage V of the electrical signal ES (V) output from the receiver 20 to the optical modulator 2, and based on the detected voltage V, the control unit 3 The wavelength λ for suppressing nonlinear distortion in the relationship between the output and the voltage V is detected by the method described above, and the laser light source 1 is controlled so as to generate laser light having the detected wavelength λ. In the light modulation device 10, the laser light source 1 generates laser light having a wavelength λ according to control from the control unit 3, and guides the generated laser light to the optical modulator 2 through the optical fiber transmission line 4. . Further, the optical modulator 2 converts the transmission intensity of the laser light from the laser light source 1 into a transmission intensity proportional to the voltage V of the electric signal ES (V) received from the receiver 20, and has the converted transmission intensity. The optical signal OS is emitted to the optical fiber transmission line 30. As a result, the optical modulation device 10 converts the electrical signal ES (V) received from the receiver 20 into an optical signal OS while suppressing nonlinear distortion, and outputs the converted optical signal OS to the optical fiber transmission line 30. .

  The optical fiber transmission line 30 transmits the optical signal OS from the light modulation device 10 to the photoelectric converter 40. The photoelectric converter 40 receives the optical signal OS from the optical fiber transmission line 30, converts the received optical signal OS into an electrical signal ES (V), and outputs the electrical signal ES (V) to the transmitter 50.

  The transmitter 50 converts the electrical signal ES (V) received from the photoelectric converter 40 into a wireless signal and transmits it to the wireless communication space.

  As described above, the relay system 100 converts the radio signal RF received by the receiver 20 from the radio communication space into the optical signal OS while suppressing nonlinear distortion, and transmits the optical signal OS to the photoelectric converter 40. The device 50 converts the optical signal OS into a wireless signal and transmits it to the wireless communication space. That is, the relay system 100 relays the radio signal RF received by the receiver 20 from the radio communication space.

[Application 2]
FIG. 7 is another schematic block diagram showing the configuration of a relay system using the optical modulation device according to the embodiment of the present invention. With reference to FIG. 7, the relay system 200 includes transceivers 210 and 260, transceiver modules 220 and 250, and optical fiber transmission lines 230 and 240.

  The transmission / reception module 220 includes a light modulation device 221 and a photoelectric converter 222. The light modulation device 221 has the same configuration as the light modulation device 10 shown in FIG. In addition, the transmission / reception module 250 includes a light modulation device 251 and a photoelectric converter 252. The light modulation device 251 has the same configuration as the light modulation device 10 shown in FIG.

  The transceiver 210 is connected to the light modulator 2 of the light modulation device 221 and the photoelectric converter 222. The optical fiber transmission line 230 connects the optical modulator 2 of the optical modulation device 221 to the photoelectric converter 252 of the transmission / reception module 250.

  The optical fiber transmission line 240 connects the optical modulator 2 of the optical modulation device 251 to the photoelectric converter 222 of the transmission / reception module 220. The transceiver 260 is connected to the light modulator 2 of the light modulation device 251 and the photoelectric converter 252.

  The transceiver 210 receives the radio signal RF1 from the radio communication space, converts the received radio communication RF1 into an electric signal ES1 (V1) composed of the voltage V1, and outputs it to the optical modulator 2 of the optical modulator 221. Further, the transceiver 210 converts the electrical signal ES2 (V2) (consisting of the voltage V2) received from the photoelectric converter 222 into a radio signal RF1 and transmits it to the radio communication space.

  The optical modulation device 221 converts the electrical signal ES1 (V1) received from the transceiver 210 into an optical signal OS1 while suppressing nonlinear distortion, and outputs the converted optical signal OS1 to the optical fiber transmission line 230.

  The photoelectric converter 222 converts the optical signal OS2 received from the optical fiber transmission line 240 into an electrical signal ES2 (V2) composed of the voltage V2, and outputs the converted electrical signal ES2 (V2) to the transceiver 210.

  The optical fiber transmission line 230 propagates the optical signal OS <b> 1 output from the light modulation device 221 to the photoelectric converter 252 of the transmission / reception module 250. The optical fiber transmission line 240 propagates the optical signal OS <b> 2 output from the light modulation device 251 of the transmission / reception module 250 to the photoelectric converter 222 of the transmission / reception module 220.

  The optical modulation device 251 converts the electrical signal ES4 (V4) (consisting of the voltage V4) received from the transceiver 260 into the optical signal OS2 while suppressing nonlinear distortion, and converts the converted optical signal OS2 into the optical fiber transmission line 240. Output to.

  The photoelectric converter 252 receives the optical signal OS1 from the optical fiber transmission line 230, converts the received optical signal OS1 into an electrical signal ES3 (V3) composed of the voltage V3, and outputs the electrical signal ES3 to the transceiver 260.

  The transceiver 260 converts the electrical signal ES3 (V3) received from the photoelectric converter 252 into a wireless signal RF2 and transmits it to the wireless communication space. Further, the transceiver 260 receives the radio signal RF2 from the radio communication space, converts the received radio signal RF2 into an electric signal ES4 (V4) composed of the voltage V4, and outputs it to the optical modulation device 251.

  The overall operation of the relay system 200 will be described. The transceiver 210 receives the radio signal RF1 from the radio communication space, converts the received radio signal RF1 into an electric signal ES1 (V1) composed of the voltage V1, and outputs the electric signal ES1 (V1) to the optical modulator 2 of the optical modulator 221. In the optical modulation device 221, the control unit 3 detects the voltage V1 of the electrical signal ES1 (V1) output from the transceiver 210 to the optical modulator 2, and based on the detected voltage V1, the control unit 3 The wavelength λ1 for suppressing nonlinear distortion in the relationship between the output and the voltage V1 is detected by the above-described method, and the laser light source 1 is controlled so as to generate laser light having the detected wavelength λ1. The laser light source 1 of the light modulation device 221 generates laser light having a wavelength λ 1 in accordance with control from the control unit 3, and guides the generated laser light to the optical modulator 2 through the optical fiber transmission line 4. Then, the optical modulator 2 converts the transmission intensity of the laser light from the laser light source 1 into a transmission intensity proportional to the voltage V1 of the electrical signal ES1 (V1) received from the transceiver 210, and has the converted transmission intensity. The optical signal OS1 is emitted to the optical fiber transmission line 230. As a result, the optical modulation device 221 converts the electrical signal ES1 (V1) received from the transceiver 210 into an optical signal OS1 while suppressing nonlinear distortion, and outputs the converted optical signal OS1 to the optical fiber transmission line 230. .

  The optical fiber transmission line 230 transmits the optical signal OS1 from the light modulation device 221 to the photoelectric converter 252. The photoelectric converter 252 receives the optical signal OS1 from the optical fiber transmission line 230, converts the received optical signal OS1 into an electrical signal ES3 (V3), and outputs the electrical signal ES3 to the transceiver 260.

  The transceiver 260 converts the electrical signal ES3 (V3) received from the photoelectric converter 252 into a wireless signal RF2 and transmits it to the wireless communication space.

  Further, the transceiver 260 receives the radio signal RF2 from the radio communication space, converts the received radio signal RF2 into an electric signal ES4 (V4) composed of the voltage V4, and outputs it to the optical modulator 2 of the optical modulation device 251. To do. In the optical modulation device 251, the control unit 3 detects the voltage V4 of the electrical signal ES4 (V4) output from the transceiver 260 to the optical modulator 2, and based on the detected voltage V4, the control unit 3 The wavelength λ2 for suppressing nonlinear distortion in the relationship between the output and the voltage V4 is detected by the method described above, and the laser light source 1 is controlled so as to generate laser light having the detected wavelength λ2. The laser light source 1 of the light modulation device 251 generates laser light having a wavelength λ 2 in accordance with control from the control unit 3, and guides the generated laser light to the optical modulator 2 via the optical fiber transmission line 4. Then, the optical modulator 2 converts the transmission intensity of the laser light from the laser light source 1 into a transmission intensity proportional to the voltage V4 of the electrical signal ES4 (V4) received from the transceiver 260, and has the converted transmission intensity. The optical signal OS2 is emitted to the optical fiber transmission line 240. Thereby, the optical modulation device 251 converts the electrical signal ES4 (V4) received from the transceiver 260 into the optical signal OS2 while suppressing nonlinear distortion, and outputs the converted optical signal OS2 to the optical fiber transmission line 240. .

  The optical fiber transmission line 240 transmits the optical signal OS2 from the light modulation device 251 to the photoelectric converter 222. The photoelectric converter 222 receives the optical signal OS2 from the optical fiber transmission line 240, converts the received optical signal OS2 into an electrical signal ES2 (V2), and outputs the electrical signal ES2 to the transceiver 210.

  The transceiver 210 converts the electrical signal ES2 (V2) received from the photoelectric converter 222 into a wireless signal RF1 and transmits it to the wireless communication space.

  As described above, the relay system 200 converts the wireless signal RF1 received from the wireless communication space by the transceiver 210 into the optical signal OS1 while suppressing nonlinear distortion in the transmission / reception module 220, and transmits the optical signal OS1 to the transmission / reception module 250. The transmitter / receiver 260 converts the optical signal OS1 into a radio signal RF2 and transmits the radio signal RF2 to the radio communication space. The signal OS2 is converted and transmitted to the transmission / reception module 220, and the transmission / reception module 220 and the transceiver 210 convert the optical signal OS2 into the radio signal RF1 and transmit it to the radio communication space. That is, the relay system 200 relays the radio signals RF1 and RF2 received from the radio communication space in both directions.

[Application Example 3]
FIG. 8 is a schematic diagram showing a configuration of a network system using the light modulation device according to the embodiment of the present invention. Referring to FIG. 8, a network system 300 includes a gateway 310, transmission / reception modules 320, 340, 360, 400, 420, optical fiber transmission lines 330, 350, 390, 410, a mobile phone 370, and a digital home appliance. 380, a wireless LAN (Local Area Network) system 430, and an AV (Audio Video) device 440.

  Gateway 310, transmission / reception modules 320, 340, 360, 400, 420, optical fiber transmission lines 330, 350, 390, 410, mobile phone 370, digital home appliance 380, wireless LAN system 430, and AV equipment 440 are in house 460. Placed in. Accordingly, the network system 300 constitutes a network in the office or home. Each of the transmission / reception modules 320, 340, 360, 400, and 420 has the same configuration as the transmission / reception modules 220 and 250 shown in FIG.

  The gateway 310 is connected to an IP (Internet Protocol) network 450. The transmission / reception module 320 is connected to the gateway 310. The optical fiber transmission line 330 connects the transmission / reception module 340 to the transmission / reception module 320. The transmission / reception module 340 has an antenna 341 and is connected to the transmission / reception module 320 via the optical fiber transmission line 330.

  The optical fiber transmission line 350 connects the transmission / reception module 360 to the transmission / reception module 340. The transmission / reception module 360 is connected to the transmission / reception module 340 via the optical fiber transmission line 350. Digital home appliance 380 is connected to transmission / reception module 360.

  The optical fiber transmission line 390 connects the transmission / reception module 400 to the transmission / reception module 320. The transmission / reception module 400 includes an antenna 401 and is connected to the transmission / reception module 320 via an optical fiber transmission line 390.

  The optical fiber transmission line 410 connects the transmission / reception module 420 to the transmission / reception module 400. The transmission / reception module 420 is connected to the transmission / reception module 400 via the optical fiber transmission line 410. The AV device 440 is connected to the transmission / reception module 420.

  The gateway 310 transmits and receives digital signals to and from the IP network 450. The gateway 310 converts the digital signal received from the IP network 450 into an analog signal and transmits the analog signal to the transmission / reception module 320. The gateway 310 converts the analog signal received from the transmission / reception module 320 into a digital signal and transmits the digital signal to the IP network 450.

  The transmission / reception module 320 converts the analog signal ANS (consisting of the voltage V) received from the gateway 310 into an optical signal OS1 while suppressing nonlinear distortion, and transmits / receives the converted optical signal OS1 via the optical fiber transmission line 330. To 340. Further, the transmission / reception module 320 converts the analog signal ANS received from the gateway 310 into the optical signal OS2 while suppressing nonlinear distortion, and transmits the converted optical signal OS2 to the transmission / reception module 400 via the optical fiber transmission line 390. . Further, the transceiver module 320 receives the optical signal OS1 from the optical fiber transmission line 330, converts the received optical signal OS1 into an analog signal ANS, and transmits the analog signal ANS to the gateway 310. Further, the transmission / reception module 320 receives the optical signal OS2 from the optical fiber transmission line 390, converts the received optical signal OS2 into an analog signal ANS, and transmits the analog signal ANS to the gateway 310.

  The optical fiber transmission line 330 transmits the optical signal OS1 between the transmission / reception modules 320 and 340. In the transmission / reception module 340, the optical modulator 2 and the photoelectric converter 222 (see FIG. 7) are connected to the antenna 341, the optical modulator 2 is connected to the optical fiber transmission lines 330 and 350, and the photoelectric converter 222 is The optical fiber transmission lines 330 and 350 are connected. Therefore, the transmission / reception module 340 receives the optical signal OS1 from the optical fiber transmission line 330 by the optical modulator 2, converts the received optical signal OS1 into the optical signal OS3 while suppressing nonlinear distortion, and transmits the optical fiber. Transmit to line 350. The transceiver module 340 receives the optical signal OS3 from the optical fiber transmission line 350 by the optical modulator 2, converts the received optical signal OS3 into the optical signal OS1 while suppressing nonlinear distortion, and transmits the optical fiber. Transmit to the line 330. Further, the transmission / reception module 340 receives the optical signal OS1 from the optical fiber transmission line 330 by the photoelectric converter 222, converts the received optical signal OS1 into an electric signal ES1 (V1) composed of the voltage V1, and transmits it to the antenna 341. Output. Further, the transmission / reception module 340 receives the optical signal OS3 from the optical fiber transmission line 350 by the photoelectric converter 222, converts the received optical signal OS3 into an electric signal ES1 (V1) composed of the voltage V1, and transmits it to the antenna 341. Output. Furthermore, the transmission / reception module 340 converts the electrical signal ES1 (V1) received from the antenna 341 into an optical signal OS1 while suppressing nonlinear distortion, and transmits the converted optical signal OS1 to the optical fiber transmission line 330. Further, the transmission / reception module 340 converts the electrical signal ES1 (V1) received from the antenna 341 into an optical signal OS3 while suppressing nonlinear distortion, and transmits the converted optical signal OS3 to the optical fiber transmission line 350.

  The antenna 341 converts the electrical signal ES1 (V1) received from the transmission / reception module 340 into a radio signal RF1 and transmits the radio signal RF1 to the mobile phone 370, receives the radio signal RF1 from the mobile phone 370, and receives the received radio signal RF1. The electric signal ES1 (V1) is converted and output to the transmission / reception module 340.

  The optical fiber transmission line 350 propagates the optical signal OS3 between the transmission / reception modules 340 and 360.

  The transmission / reception module 360 receives the optical signal OS3 from the optical fiber transmission line 350, converts the received optical signal OS3 into an electric signal ES2 (V2) composed of the voltage V2, and transmits it to the digital home appliance 380. In addition, the transmission / reception module 360 converts the electrical signal ES2 (V2) received from the digital home appliance 380 into an optical signal OS3 while suppressing nonlinear distortion, and outputs the converted optical signal OS3 to the optical fiber transmission line 350.

  The cellular phone 370 transmits and receives a radio signal RF1 to and from the antenna 341. The digital home appliance 380 performs signal processing on the electrical signal ES2 (V2) received from the transmission / reception module 360 and performs a predetermined operation.

  The optical fiber transmission line 390 propagates the optical signal OS2 between the transmission / reception modules 320 and 440. In the transceiver module 400, the optical modulator 2 and the photoelectric converter 222 (see FIG. 7) are connected to the antenna 401, the optical modulator 2 is connected to the optical fiber transmission lines 390 and 410, and the photoelectric converter 222 is The optical fiber transmission lines 390 and 410 are connected. Accordingly, the transmission / reception module 400 receives the optical signal OS2 from the optical fiber transmission line 390 by the optical modulator 2, and converts the received optical signal OS2 into the optical signal OS4 while suppressing nonlinear distortion, and transmits the optical fiber. Transmit to line 410. Also, the transceiver module 400 receives the optical signal OS4 from the optical fiber transmission line 410 by the optical modulator 2, and converts the received optical signal OS4 into the optical signal OS2 while suppressing nonlinear distortion to transmit the optical fiber. Transmit to line 390. Further, the transmission / reception module 400 receives the optical signal OS2 from the optical fiber transmission line 390 by the photoelectric converter 222, converts the received optical signal OS2 into an electric signal ES3 (V3) composed of the voltage V3, and transmits it to the antenna 401. Output. Further, the transmission / reception module 400 receives the optical signal OS4 from the optical fiber transmission line 410 by the photoelectric converter 222, converts the received optical signal OS4 into an electric signal ES3 (V3) composed of the voltage V3, and transmits it to the antenna 401. Output. Further, the transmission / reception module 400 converts the electrical signal ES3 (V3) received from the antenna 401 into an optical signal OS2 while suppressing nonlinear distortion, and transmits the converted optical signal OS2 to the optical fiber transmission line 390. Furthermore, the transceiver module 400 converts the electrical signal ES3 (V3) received from the antenna 401 into an optical signal OS4 while suppressing nonlinear distortion, and transmits the converted optical signal OS4 to the optical fiber transmission line 10.

  The antenna 401 converts the electrical signal ES3 (V3) received from the transmission / reception module 400 into a wireless signal RF2 and transmits it to the wireless LAN system 430, receives the wireless signal RF2 from the wireless LAN system 430, and receives the received wireless signal. RF2 is converted into an electrical signal ES3 (V3) and output to the transceiver module 400.

  The optical fiber transmission line 410 propagates the optical signal OS4 between the transmission / reception modules 400 and 420.

  The transmission / reception module 420 receives the optical signal OS4 from the optical fiber transmission line 410, converts the received optical signal OS4 into an electrical signal ES4 (V4) composed of the voltage V4, and transmits the electrical signal ES4 to the AV device 440. Further, the transmission / reception module 420 converts the electrical signal ES4 (V4) received from the AV device 440 into an optical signal OS4 while suppressing nonlinear distortion, and outputs the converted optical signal OS4 to the optical fiber transmission line 410.

  The wireless LAN system 430 transmits and receives a wireless signal RF2 to and from the antenna 401. The AV device 440 performs signal processing of the electrical signal ES4 (V4) received from the transmission / reception module 420, and gives audio or video to the user.

  An operation in which the mobile phone 370 communicates with the IP network 450 will be described. The cellular phone 370 transmits the radio signal RF1 to the antenna 341. The antenna 341 receives the radio signal RF1 from the cellular phone 370, converts the received radio signal RF1 into an electric signal ES1 (V1), and transmits / receives the transmission / reception module 340. Output to.

  Then, in the transmission / reception module 340, the light modulation device 221 (see FIG. 7) converts the electrical signal ES1 (V1) from the antenna 341 into an optical signal OS1 while suppressing nonlinear distortion, and the converted optical signal OS1 is converted into an optical signal. The data is transmitted to the transmission / reception module 320 via the fiber transmission line 330.

  The transceiver module 320 receives the optical signal OS1 from the transceiver module 340 via the optical fiber transmission line 330 by the photoelectric converter 222 (see FIG. 7), converts the received optical signal OS1 into an analog signal ANS, and is a gateway. To 310. Then, the gateway 310 converts the analog signal ANS into a digital signal and transmits it to the IP network 450.

  Thereafter, when receiving a digital signal from the IP network 450, the gateway 310 converts the received digital signal into an analog signal ANS and transmits the analog signal ANS to the transmission / reception module 320. The transmission / reception module 320 converts the analog signal ANS received from the gateway 310 into the optical signal OS1 while suppressing nonlinear distortion, and transmits the converted optical signal OS1 to the transmission / reception module 340 via the optical fiber transmission line 330. .

  The transceiver module 340 receives the optical signal OS1 from the transceiver module 320 via the optical fiber transmission line 330, converts the received optical signal OS1 into an electrical signal ES1 (V1), and outputs the electrical signal ES1 to the antenna 341. Then, the antenna 341 converts the electrical signal ES1 (V1) into a radio signal RF1 and transmits it to the mobile phone 370, and the mobile phone 370 receives the radio signal RF1 from the antenna 341.

  In this way, the mobile phone 370 communicates with the IP network 450.

  Digital home appliance 380, wireless LAN system 430, and AV device 440 also communicate with IP network 450 according to the same operation as mobile phone 370.

  Next, an operation for performing communication between the mobile phone 370 and the digital home appliance 380 will be described. The cellular phone 370 transmits the radio signal RF1 to the antenna 341. The antenna 341 receives the radio signal RF1 from the cellular phone 370, converts the received radio signal RF1 into an electric signal ES1 (V1), and transmits / receives the transmission / reception module 340. Output to.

  Then, in the transmission / reception module 340, the light modulation device 221 (see FIG. 7) converts the electrical signal ES1 (V1) from the antenna 341 into an optical signal OS3 while suppressing nonlinear distortion, and the converted optical signal OS3 is converted into an optical signal. The data is transmitted to the transmission / reception module 360 via the fiber transmission line 350.

  The transmission / reception module 360 receives the optical signal OS3 from the transmission / reception module 340 via the optical fiber transmission line 350 by the photoelectric converter 222 (see FIG. 7), and converts the received optical signal OS3 into an electrical signal ES2 (V2). To the digital home appliance 380.

  Thereafter, the digital home appliance 380 transmits the electrical signal ES2 (V2) to the transmission / reception module 360. Then, the transmission / reception module 360 converts the electrical signal ES2 (V2) received from the digital home appliance 380 into an optical signal OS3 while suppressing nonlinear distortion, and transmits / receives the converted optical signal OS3 via the optical fiber transmission line 350. Transmit to module 340.

  The transceiver module 340 receives the optical signal OS3 from the transceiver module 360 via the optical fiber transmission line 350, converts the received optical signal OS3 into an electrical signal ES1 (V1), and outputs the electrical signal ES1 to the antenna 341. Then, the antenna 341 converts the electrical signal ES1 (V1) into a radio signal RF1 and transmits it to the mobile phone 370, and the mobile phone 370 receives the radio signal RF1 from the antenna 341.

  In this manner, the mobile phone 370 communicates with the digital home appliance 380.

  The mobile phone 370, the digital home appliance 380, the wireless LA system 430, and the AV device 440 communicate with each other by the same method as the communication between the mobile phone 370 and the digital home appliance 380 described above.

  As described above, the mobile phone 370, the digital home appliance 380, the wireless LA system 430, and the AV device 440 installed in the office or home communicate with the IP network 450 and communicate with each other. Accordingly, services such as a mobile phone, a wireless LAN, and television broadcasting can be received everywhere in the house 460.

  In such various services, it is necessary to convert electrical signals having various frequency bands into optical signals while suppressing nonlinear distortion. However, the transmission / reception modules 320, 340, 360, 400, and 420 are nonlinear. Since the electrical signal is converted into the optical signal while suppressing the distortion, the network system 300 can perform communication by converting the electrical signal composed of various frequency bands into the optical signal while suppressing the nonlinear distortion.

  Further, since the transmission / reception modules 320, 340, 360, 400, and 420 have the same configuration, they are connected to the mobile phone 370, the digital home appliance 380, the wireless LAN 430, and the AV device 440 that transmit and receive signals having different frequencies. Even when the transmission / reception module is disposed in the network system 300, it is not necessary to prepare transmission / reception modules respectively corresponding to the mobile phone 370, the digital home appliance 380, the wireless LAN 430, and the AV device 440, and the network system 300 can be easily constructed.

  Gateway 310 constitutes a “communication device”.

  In addition, the mobile phone 370, the digital home appliance 380, the wireless LAN 430, and the AV device 440 constitute a “communication device”.

  Further, the transmission / reception module 320 constitutes a “first transmission / reception module”, and each of the transmission / reception modules 340, 360, 400, 420 constitutes a “second transmission / reception module”.

[Application Example 4]
FIG. 9 is a schematic diagram showing a configuration of an optical modulation adjusting apparatus using the optical modulation apparatus according to the embodiment of the present invention. Referring to FIG. 9, a light modulation adjusting device 500 is obtained by adding a receiver 11, an optical fiber transmission line 12, and a photoelectric converter 13 to the light modulating device 10 shown in FIG. 10 is the same.

  In the light modulation adjustment device 500, the output side of the light modulator 2 is connected to the optical fiber transmission line 5.

  The receiver 11 is connected to the light modulator 2 of the light modulation device 10. The optical fiber transmission line 12 has one end connected to the optical fiber transmission line 5 and the other end connected to the photoelectric converter 13. The photoelectric converter 13 is connected to the control unit 3 of the light modulation device 10.

For example, the receiver 11 outputs an electrical signal ES1 including a component ES1 (f1) having a frequency band f1 and a component ES1 (f2) having a frequency band f2 to the optical modulator 2. The optical fiber transmission line 12 guides a part OS _prt of the optical signal OS emitted from the optical modulator 2 to the optical fiber transmission line 5 to the photoelectric converter 13. The photoelectric converter 13 converts a part OS _prt of the optical signal OS received from the optical fiber transmission line 12 into an electric signal ES2 having a voltage V, and outputs the electric signal ES2 to the control unit 3 of the light modulation device 10.

  FIG. 10 is a schematic diagram showing the configuration of the control unit 3 shown in FIG. Referring to FIG. 10, control unit 3 includes band pass filters (BPF: Band Pass Filter) 31, 32, power detection units 33, 34, and loop filter 35.

  The power detection units 33 and 34 are provided corresponding to the BPFs 31 and 32 and are connected to the BPFs 31 and 32, respectively. The loop filter 35 is connected to the power detection units 33 and 34.

  The optical signal OS output from the optical modulator 2 includes a plurality of components OS (f1) and OS (f2). Each of the plurality of components OS (f1) and OS (f2) includes a pilot tone for detecting second-order distortion and third-order distortion.

  Each of the BPFs 31 and 32 receives the electrical signal ES <b> 2 from the photoelectric conversion unit 13. This electrical signal ES2 includes a component of frequency f1, a component of frequency f2, a secondary component of frequency f1 (= 2f1), a tertiary component of frequency f1 (= 3f1), a secondary component of frequency f2 (= 2f2), and a frequency It includes a third-order component of f2 (= 3f2), a second-order component of frequencies f1 and f2 (= f1 ± f2), and a third-order component of frequencies f1 and f2 (= 2f1 ± f2, 2f2 ± f1).

  Then, the BPF 31 transmits only the secondary component (= 2f1) of the frequency f1 among the eight components of the electrical signal ES2 to the power detection unit 33. The BPF 32 transmits only the third-order components (= 2f1-f2) of the frequencies f1 and f2 among the eight components of the electric signal ES2 to the power detection unit 34.

  The power detection unit 33 detects the power PW1 of the secondary component (= 2f1) of the frequency f1 and outputs the detected power PW1 to the loop filter 35. The power detection unit 34 detects the power PW2 of the third order component (= 2f1-f2) of the frequencies f1 and f2, and outputs the detected power PW2 to the loop filter 35.

  Loop filter 35 receives electric powers PW1 and PW2 from electric power detection units 33 and 34, respectively. Then, the loop filter 35 determines a control value for suppressing the second-order distortion and the third-order distortion based on the electric powers PW1 and PW2, and supplies the determined control value to the laser light source 1. Output.

  FIG. 11 is a conceptual diagram of frequency components of an electric signal. Referring to FIG. 11, components SS1 and SS2 are signal components, and have frequencies f1 and f2, respectively. Components SS3 to SS5 are second-order distortions, and have frequencies 2f1, 2f2, and f1 + f2, respectively. Components SS6 and SS7 are third-order distortions, and have frequencies 2f1-f2 and 2f2-f1, respectively.

  In the present invention, the pilot signal PLT1 is set to the component SS3 (frequency 2f1) among the components SS3 to SS5 indicating the second-order distortion, and the component SS6 (frequency 2f1-f2 is selected from the components SS6 and SS7 indicating the third-order distortion. ) Is set to pilot signal PLT2.

Assuming that the current wavelength is λ, the second-order distortion and the third-order distortion are the second-order and third-order expressions for the wavelength λ, respectively. Therefore, the power of the second-order distortion and the power of the third-order distortion are | It is proportional to λ ² | and | λ ³ |.

  FIG. 12 is a diagram illustrating the relationship between the power and wavelength of nonlinear distortion. In FIG. 12, the vertical axis represents nonlinear distortion power, and the horizontal axis represents wavelength. A curve k14 shows the relationship between the second order distortion and the wavelength, and a curve k15 shows the relationship between the third order distortion and the wavelength. Further, λ0 is a control target value.

Referring to FIG. 12, the second-order distortion power is proportional to | λ ² | (see curve k14), and the third-order distortion power is proportional to | λ ³ | (see curve k15). The power of the second-order distortion and the power of the third-order distortion are minimum when the wavelength is λ0 (= control target value). In the present invention, when the wavelength is λ0, the second order distortion and the third order distortion are eliminated.

  When the wavelength deviates from λ0, the second-order distortion power and the third-order distortion power monotonously increase. That is, when the wavelength deviates from λ0, nonlinear distortion increases.

  Therefore, the second-order distortion power PW1 and the third-order distortion power PW2 are detected, and the detected second-order distortion power PW1 and third-order distortion power PW2 are the power PW02 (second-order distortion when the wavelength is λ0). ) And power PW03 (power of third-order distortion when the wavelength is λ0), the wavelength is brought close to λ0.

  In this case, the power detection eves 33 and 34 detect the powers PW1 and PW2, respectively, and output the detected powers PW1 and PW2 to the loop filter 35. When the power PW1 and PW2 increase, the loop filter 35 detects the wavelength λ for bringing the power PW1 and PW2 closer to the power PW02 and the power PW03 with reference to the curves k14 and k15, and has the detected wavelength λ. The laser light source 1 is controlled so as to generate laser light.

  FIG. 13 is a flowchart for explaining the adjustment operation in the light modulation adjustment apparatus 500 shown in FIG. In FIG. 13, shifting the wavelength λ to the long wavelength side (right side in FIG. 12) is referred to as “shifting the wavelength in the positive direction”, and the wavelength λ is shifted to the short wavelength side (left side in FIG. 12). Shifting is called “shifting the wavelength in the negative direction”.

  Referring to FIG. 13, when a series of operations is started, loop filter 35 sets wavelength λ to initial value λ1 (step S1). Then, the loop filter 35 sets the wavelength λ to a wavelength λm longer or shorter than the initial value λ1, and controls the laser light source 1 so as to generate laser light having the set wavelength λm. That is, the wavelength λ is shifted to either positive or negative (step S2).

  The laser light source 1 generates laser light having a wavelength λm according to the control of the loop filter 35, and guides the generated laser light to the optical modulator 2 through the optical fiber transmission line 4. The receiver 11 generates an electric signal ES1 in which pilot signals PLT1 and PLT2 are set to frequencies 2f1, 2f2-f1, and outputs the electric signal ES1 to the optical modulator 2.

  The optical modulator 2 converts the electric signal ES1 into an optical signal OS by converting the transmission intensity of the laser light from the laser light source 1 into a transmission intensity corresponding to the voltage constituting the electric signal ES1, and the converted optical signal The OS is output to the optical fiber transmission line 5.

The optical fiber transmission line 12 guides a part OS _prt of the optical signal OS propagating through the optical fiber transmission line 5 to the photoelectric conversion unit 13. Then, the photoelectric conversion unit 13 converts a part OS _prt of the optical signal OS received from the optical fiber transmission line 12 into an electric signal ES2 composed of the voltage V, and outputs it to the control unit 3 of the light modulation device 10.

  Then, in the control unit 3, the BPF 31 transmits only the component SS3 having the frequency 2f1 in the electric signal ES2 to the power detection unit 33, and the BPF 32 only has the component SS6 having the frequency 2f2-f1 in the electric signal ES2. Is transmitted to the power detector 34. The power detection unit 33 detects the power PW1 of the component SS3 and outputs it to the loop filter 35, and the power detection unit 34 detects the power PW2 of the component SS3 and outputs it to the loop filter 35. Thereby, the amount of distortion is detected (step S3).

  Thereafter, the loop filter 35 determines whether or not the amount of distortion has increased based on the powers PW1 and PW2 (step S4). More specifically, the loop filter 35 determines that the amount of distortion has increased when the power PW1, PW2 is increasing, and determines that the amount of distortion has decreased when the power PW1, PW2 has decreased. .

  When it is determined in step S4 that the amount of distortion has increased, the loop filter 35 shifts the wavelength λ in the direction opposite to the direction shifted in step S2 (step S5), and the laser beam having the shifted wavelength. The laser light source 1 is controlled so as to generate. Then, a series of operation | movement transfers to step S7 mentioned later.

  On the other hand, when it is determined in step S4 that the amount of distortion has not increased, the loop filter 35 shifts the wavelength λ in the same direction as that shifted in step S2 (step S6), and the shifted wavelength. The laser light source 1 is controlled so as to generate laser light having

After step S5 or step S6, the laser light source 1 generates laser light having a predetermined wavelength and guides it to the optical modulator 2 according to the control from the loop filter 35, and the optical modulator 2 transmits the electric signal ES1 to the optical signal ES1. The photoelectric converter 13 converts a part OS _prt of the optical signal OS into an electric signal ES2, and the BPF 31, BPF 32 and the power detection units 33, 34 of the control unit 3 are distorted by the above-described operation. The amount is detected (step S7).

  Then, the loop filter 35 determines whether or not the distortion amount has reached a target value (for example, power PW02, PW03) (step S8). When the distortion amount has not reached the target value, the series of operations returns to step S4, and the above-described steps S4 to S8 are repeated until it is determined in step S8 that the distortion amount has reached the target value. Executed.

  If it is determined in step S8 that the amount of distortion has reached the target value, the series of operations ends.

  In this way, the light modulation adjustment device 500 detects nonlinear distortion (= second-order distortion and third-order distortion) of the optical signal emitted from the light modulation apparatus 10, and the laser so that the detected nonlinear distortion is eliminated. The wavelength λ generated by the light source 1 is adjusted. As a result, the light modulation device 10 can be adjusted so as to eliminate the non-linear distortion (= second order distortion and third order distortion) and convert the electric signal into an optical signal.

  In the above description, a configuration has been described in which second-order distortion and third-order distortion are detected by detecting the power of pilot signals set in two frequency bands. However, the present invention is not limited to this. Second-order distortion and third-order distortion may be detected by detecting the power of pilot signals set in more than one frequency band. In this case, the control unit 3 includes n BPFs according to the number n of pilot signals to be set (n is an integer of 3 or more), and n power detection units provided according to the n BPFs. And one loop filter. The control unit 3 detects the second-order distortion and the third-order distortion by the method described above, and sets a control value (= wavelength λ) for suppressing the detected second-order distortion and third-order distortion to the control target value. The laser light source 1 is controlled so as to generate laser light having the determined wavelength λ.

[Application Example 5]
FIG. 14 is another schematic diagram showing the configuration of an optical modulation adjustment apparatus using the optical modulation apparatus according to the embodiment of the present invention. Referring to FIG. 14, the light modulation adjustment apparatus 600 includes a transmission module 610, optical fiber transmission lines 620 and 630, and a reception module 640.

  The transmission module 610 includes a light modulation device 611 and a photoelectric converter 612. The reception module 640 includes a photoelectric converter 641, a distortion detector 642, an optical modulator 643, a laser light source 644, and an optical fiber transmission line 645.

  The light modulation device 611 has the same configuration as the light modulation device 10 shown in FIG. The photoelectric converter 612 is connected to the control unit 3 of the light modulation device 611 and the transceiver 650.

  The optical fiber transmission line 620 has one end connected to the optical modulator 2 of the light modulation device 611 and the other end connected to the photoelectric converter 641 of the receiving module 640. The optical fiber transmission line 630 has one end connected to the photoelectric converter 612 of the transmission module 610 and the other end connected to the optical modulator 643 of the reception module 640.

  The photoelectric converter 641 is connected to the distortion detector 642 and the transceiver 660. The distortion detector 642 is connected to the photoelectric converter 641, the optical modulator 643, and the transceiver 660. The optical modulator 643 is connected to the photoelectric conversion unit 612 of the transmission module 610 by the optical fiber transmission line 630 and is connected to the laser light source 644 by the optical fiber transmission line 645.

  The transceiver 650 receives the radio signal RF1 from the radio communication space, converts the received radio communication RF1 into an electric signal ES1 (V1) composed of the voltage V1, and outputs the electric signal ES1 (V1) to the optical modulator 2 of the optical modulation device 611. Further, the transceiver 650 converts the electrical signal ES2 (V2) (consisting of the voltage V2) received from the photoelectric converter 612 into a radio signal RF1 and transmits the radio signal RF1 to the radio communication space.

  The optical modulation device 611 converts the electrical signal ES1 (V1) received from the transceiver 650 into an optical signal OS1 while suppressing nonlinear distortion, and outputs the converted optical signal OS1 to the optical fiber transmission line 620.

  The photoelectric converter 612 converts the optical signal OS2 received from the optical fiber transmission line 630 into an electric signal ES2 (V2) composed of the voltage V2, and outputs the converted electric signal ES2 (V2) to the transceiver 650.

  The optical fiber transmission line 620 propagates the optical signal OS1 output from the light modulation device 611 to the photoelectric converter 641 of the reception module 640. The optical fiber transmission line 630 propagates the optical signal OS2 output from the optical modulator 643 of the reception module 640 to the photoelectric converter 612 of the transmission module 610.

  The optical modulator 643 receives the electrical signal ES4 (V4) (consisting of the voltage V4) from the transceiver 660, and receives a control value (= wavelength λ) for correcting the distortion from the distortion detector 643. Then, the optical modulator 643 superimposes the control value for correcting the distortion on the electrical signal ES4 (V4) as a pilot signal, converts the electrical signal ES4 (V4) on which the control value is superimposed into the optical signal OS2, The converted optical signal OS2 is output to the optical fiber transmission line 630.

  The photoelectric converter 641 receives the optical signal OS1 from the optical fiber transmission line 620, converts the received optical signal OS1 into an electrical signal ES3 (V3) composed of the voltage V3, and outputs the electrical signal ES3 to the transceiver 660.

  The transceiver 660 converts the electrical signal ES3 (V3) received from the photoelectric converter 641 into a wireless signal RF2 and transmits it to the wireless communication space. The transceiver 660 receives the radio signal RF2 from the radio communication space, converts the received radio signal RF2 into an electric signal ES4 (V4) composed of the voltage V4, and outputs the electric signal ES4 to the optical modulator 643.

  The distortion detector 642 detects the distortion contained in the electrical signal ES3 (V3) obtained by converting the optical signal OS1 and corrects the detected distortion by the same method as the controller 3 shown in FIGS. And a control value (= wavelength λ) is generated and output to the optical modulator 643.

  The laser light source 644 generates laser light having a predetermined wavelength and guides the generated laser light to the optical modulator 643.

  The overall operation of the light modulation adjustment apparatus 600 will be described. The transceiver 650 receives the radio signal RF1 from the radio communication space, converts the received radio signal RF1 into an electrical signal ES1 (V1) composed of the voltage V1, and outputs the electrical signal ES1 (V1) to the optical modulator 2 of the optical modulation device 611. In the light modulation device 611, the laser light source 1 generates laser light having a predetermined wavelength and guides it to the light modulator 2, and the light modulator 2 determines the transmission intensity of the laser light from the laser light source 1 from the transceiver 650. The received electrical signal ES1 (V1) is converted into a transmission intensity proportional to the voltage V1, and an optical signal OS1 having the converted transmission intensity is emitted to the optical fiber transmission line 620.

  The optical fiber transmission line 620 transmits the optical signal OS1 from the light modulation device 611 to the photoelectric converter 641. The photoelectric converter 641 receives the optical signal OS1 from the optical fiber transmission line 620, converts the received optical signal OS1 into an electrical signal ES3 (V3), and outputs the electrical signal ES3 to the transceiver 660 and the distortion detector 642.

  The distortion detection unit 642 detects nonlinear distortion (second-order distortion and third-order distortion) by the above-described method and corrects the detected nonlinear distortion (second-order distortion and third-order distortion) (= wavelength). λ) is determined and output to the optical modulator 643. The transceiver 660 converts the electrical signal ES3 (V3) received from the photoelectric converter 641 into a wireless signal RF2 and transmits it to the wireless communication space.

  The transceiver 660 receives the radio signal RF2 from the radio communication space, converts the received radio signal RF2 into an electric signal ES4 (V4) composed of the voltage V4, and outputs the electric signal ES4 to the optical modulator 643. The laser light source 644 generates laser light having a predetermined wavelength, and guides the generated laser light to the optical modulator 643 via the optical fiber transmission line 645. Then, the optical modulator 643 superimposes the control value (= wavelength) from the distortion detector 642 on the electrical signal ES4 (V4), and based on the laser light received from the laser light source 644, the electrical modulator that superimposes the control value. The signal ES4 (V4) is converted into an optical signal OS2, and the converted optical signal OS2 is emitted to the optical fiber transmission line 630.

  The optical fiber transmission line 630 transmits the optical signal OS2 from the optical modulator 643 to the photoelectric converter 612. The photoelectric converter 612 receives the optical signal OS2 from the optical fiber transmission line 630, converts the received optical signal OS2 into an electric signal ES2 (V2), and the transmitter / receiver of the light modulation device 611. To 650.

  The transceiver 650 converts the electrical signal ES2 (V2) received from the photoelectric converter 612 into a wireless signal RF1 and transmits it to the wireless communication space. In the light modulation device 611, the control unit 3 detects a control value (= wavelength λ) included as a pilot signal in the electrical signal ES2 (V2), and generates a laser beam having the detected wavelength λ. Thus, the laser light source 1 is controlled. The laser light source 1 generates laser light having a wavelength λ and guides it to the optical modulator 2 in accordance with control from the control unit 3.

  By repeating the above-described operation, the laser light source 1 of the light modulation device 611 causes the nonlinear distortion (= second-order distortion and third-order distortion) when the optical modulator 2 converts the electric signal ES1 (V1) into the optical signal OS1. ) Is adjusted to generate a laser beam having a wavelength λ0 for setting the target value.

  The optical modulation adjustment apparatus 600 detects nonlinear distortion (= second order distortion and third order distortion) by the receiving module 640 and corrects the detected nonlinear distortion (= second order distortion and third order distortion). A control value (= wavelength λ) is determined and transmitted to the transmission module 610. In the transmission module 610, laser light generated by the laser light source 1 so that nonlinear distortion (= second order distortion and third order distortion) becomes a target value. The wavelength is adjusted.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to an optical modulation device that can simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion. Further, the present invention is applied to a relay system including an optical modulation device that can simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion. Furthermore, the present invention is applied to a network system including an optical modulation device that can simultaneously suppress second-order nonlinear distortion and third-order nonlinear distortion.

It is a schematic block diagram which shows the structure of the light modulation apparatus by embodiment of this invention. It is a figure which shows the relationship between the optical output and bias voltage in the electro-absorption type optical modulator used for experiment. It is a figure which shows the relationship between the optical output of an electro-absorption optical modulator when changing a wavelength, and a bias voltage. It is a figure which shows the relationship between the optical output of an electro-absorption type optical modulator when a bias voltage is changed, and a wavelength. It is a figure which shows the relationship between the wavelength shift and RF voltage when the relationship between bias voltage V and wavelength (lambda) in Formula (9) is calculated | required by numerical calculation. It is a schematic block diagram which shows the structure of the relay system using the optical modulation apparatus by embodiment of this invention. It is another schematic block diagram which shows the structure of the relay system using the optical modulation apparatus by embodiment of this invention. It is the schematic which shows the structure of the network system using the optical modulation apparatus by embodiment of this invention. It is the schematic which shows the structure of the light modulation adjustment apparatus using the light modulation apparatus by embodiment of this invention. It is the schematic which shows the structure of the control part shown in FIG. It is a conceptual diagram of the frequency component of an electric signal. It is a figure which shows the relationship between a nonlinear distortion and a wavelength. 10 is a flowchart for explaining an adjustment operation in the light modulation adjustment apparatus shown in FIG. 9. It is another schematic diagram showing a configuration of a light modulation adjusting device using the light modulating device according to the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,644 Laser light source, 2,643 Optical modulator, 3 Control part, 4, 5, 12, 30, 230, 240, 330, 350, 390, 410, 620, 630, 645 Optical fiber transmission line 10,221 , 251, 611 Light modulation device, 11, 20 Receiver, 13, 40, 222, 252, 612, 641 Photoelectric converter, 31, 32 BPF, 33, 34 Power detection unit, 35 loop filter, 50 transmitter, 100 , 200 relay system, 210, 260, 650, 660 transceiver, 220, 250 320, 340, 360, 400, 420 transceiver module, 300 network system, 310 gateway, 341, 401 antenna, 370 mobile phone, 380 digital home appliance, 430 Wireless LAN, 440 AV equipment, 450 IP network, 460 house, 500,600 light modulation adjustment device, 610 transmission module, 640 reception module, 642 distortion detection unit.

Claims (10)

A light modulator that sets the transmission intensity of incident light to a transmission intensity proportional to the applied voltage, and outputs it;
Optical modulation comprising: a light source that generates a laser beam having a wavelength that suppresses nonlinear distortion in the relationship between the output of the optical modulator and the applied voltage; and that guides the generated laser beam to the optical modulator as the incident light apparatus. The nonlinear distortion is detected based on the output of the optical modulator, the wavelength for suppressing the detected nonlinear distortion is detected, and the light source is controlled to emit laser light having the detected wavelength. Further comprising control means,
The light modulation device according to claim 1, wherein the light source generates laser light having the detected wavelength in accordance with control from the control unit and guides the laser light to the optical modulator.   The control means holds a table indicating a relationship between a shift amount of the wavelength of the laser beam to be shifted to suppress the nonlinear distortion and the applied voltage. When the nonlinear distortion is detected, the table is displayed. The light modulation device according to claim 2, wherein the shift amount is detected with reference to detect a wavelength for suppressing the nonlinear distortion based on the detected shift amount. A receiver that receives a radio signal, converts the received radio signal into an electrical signal composed of a voltage, and outputs the electrical signal;
An optical modulator that converts an electrical signal from the receiver into an optical signal and outputs the optical signal;
An optical fiber transmission line for transmitting an optical signal output from the light modulation device;
The optical signal transmitted by the optical fiber transmission line is converted into an electrical signal, and a transmitter that radiates the converted electrical signal as a radio signal is provided.
The light modulation device comprises:
An optical modulator that sets the transmission intensity of incident light to a transmission intensity proportional to the voltage constituting the electrical signal and outputs the transmission intensity to the optical fiber transmission line;
A relay that includes a laser beam having a wavelength that suppresses nonlinear distortion in a relationship between an output of the optical modulator and the electrical signal, and a light source that guides the generated laser beam to the optical modulator as the incident light. system. The first radio signal is received from the radio communication space, the received first radio signal is converted into a first electric signal composed of a first voltage, and the second electric signal is converted into the first electric signal. A first transceiver for converting to a wireless signal and transmitting to the wireless communication space;
The first electrical signal from the first transceiver is converted to a first optical signal and output, and the second optical signal is converted to the second electrical signal to the first transceiver. A first transmission / reception module for outputting;
A first optical fiber transmission line for transmitting the first optical signal output from the first optical modulation device;
The first optical signal transmitted by the first optical fiber transmission line is converted into a third electric signal, the converted third electric signal is output, and the fourth electric signal composed of the second voltage is output. A second transmission / reception module that converts a signal into the second optical signal and outputs the second optical signal;
The third electrical signal is converted into a second wireless signal and transmitted to the wireless communication space, the second wireless signal is received from the wireless communication space, and the received second wireless signal is converted to the received wireless signal. A second transceiver for converting to a fourth electrical signal and outputting to the second transceiver module;
A second optical fiber transmission line that transmits the second optical signal output from the second transceiver module to the first transceiver module;
The first transmission / reception module includes:
A first optical modulation device that converts the first electrical signal into the first optical signal and outputs the first optical signal to the first optical fiber transmission line;
A first photoelectric converter that converts the second optical signal into the second electrical signal;
The second transmission / reception module includes:
A second photoelectric converter that converts the first optical signal into the third electrical signal;
A second optical modulation device that converts the fourth electrical signal into the second optical signal,
The first light modulation device includes:
A first optical modulator configured to set a transmission intensity of the first incident light to a transmission intensity proportional to a first voltage constituting the first electric signal and output the transmission intensity to the first optical fiber transmission line;
A first laser beam having a first wavelength that suppresses nonlinear distortion in a relationship between the output of the first optical modulator and the first voltage is generated, and the generated first laser beam is converted into the first laser beam. A first light source that leads to the first light modulator as one incident light,
The second light modulation device includes:
A second optical modulator that sets a transmission intensity of the second incident light to a transmission intensity proportional to a second voltage constituting the fourth electric signal and outputs the transmission intensity to the second optical fiber transmission line;
A second laser beam having a second wavelength for suppressing nonlinear distortion in a relationship between the output of the second optical modulator and the second voltage is generated, and the generated second laser beam is converted into the first laser beam. A relay system comprising: a second light source that guides the second incident light to the second light modulator. A communication device that transmits and receives digital signals to and from a communication network, and converts the digital signal received from the communication network into a first analog signal having a first voltage;
A communication device for communicating with the communication device;
The first analog signal received from the communication device is converted into an optical signal and output, and the optical signal is received, and the received optical signal is converted into the first analog signal and output to the communication device. A first transmission / reception module,
The optical signal is received, the received optical signal is converted into a second analog signal composed of a second voltage and output, and the second analog signal is converted into the optical signal to the communication device. A second transmitting / receiving module for outputting;
An optical fiber transmission line for transmitting the optical signal between the first and second transmission / reception modules;
The first transmission / reception module includes:
A first optical modulation device that converts the first analog signal into the optical signal and outputs the optical signal to the optical fiber transmission line;
A first photoelectric converter that converts the optical signal into the first analog signal;
The second transmission / reception module includes:
A second photoelectric converter that converts the optical signal into the second analog signal;
A second optical modulation device that converts the second analog signal into the optical signal and outputs the optical signal to the optical fiber transmission line;
The first light modulation device includes:
A first optical modulator that sets a transmission intensity of the first incident light to a transmission intensity proportional to a first voltage constituting the first analog signal and outputs the transmission intensity to the optical fiber transmission line;
A first laser beam having a first wavelength that suppresses nonlinear distortion in a relationship between the output of the first optical modulator and the first voltage is generated, and the generated first laser beam is converted into the first laser beam. A first light source that leads to the first light modulator as one incident light,
The second light modulation device includes:
A second optical modulator that sets a transmission intensity of the second incident light to a transmission intensity proportional to a second voltage constituting the second analog signal and outputs the transmission intensity to the optical fiber transmission line;
A second laser beam having a second wavelength for suppressing nonlinear distortion in a relationship between the output of the second optical modulator and the second voltage is generated, and the generated second laser beam is converted into the first laser beam. A network system comprising: a second light source that guides the second incident light to the second light modulator.   The network system according to claim 6, wherein the communication device, the communication device, the first and second transmission / reception modules, and the optical fiber transmission line are arranged in a house.   The network system according to claim 7, wherein the communication device includes at least one of a digital home appliance and an AV device.   The network system according to claim 7, wherein the communication device is a wireless device that performs wireless communication with the second transmission / reception module.   The network system according to claim 7, wherein the communication device includes at least one of a wireless device, a digital home appliance, and an AV device that perform wireless communication with the second transmission / reception module.

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