Demodulator and optical communication device

Abstract

To optimize a demodulation signal.SOLUTION: An ONU (Optical Network Unit) 100 has: a communication unit 110 that receives an optical signal that is an FM signal; a reception power measurement unit 140 that measures an optical power of the optical signal as a first reception power; a demodulation unit 120 that demodulates an electric signal obtained by converting the optical signal, on the basis of a parameter; and a control unit 150 that stores a setting table 151 indicating a correspondence between a reception power and the parameter, and a reception power measured in the past, compares the reception power measured in the past with the first reception power, and in a case where the reception power fluctuates, specifies a parameter according to the first reception power on the basis of the setting table 151, and sets the specified parameter in the demodulation unit 120.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure provides: a demodulator, and This relates to optical communication devices. [Background technology]

[0002] Optical communication systems are known. For example, Patent Document 1 describes an optical communication system. An optical communication system may include an optical communication device (also called a parent station device) installed in a telecommunications carrier's office (also called a parent station side) and a plurality of optical communication devices (also called child station devices) installed on a subscriber side (also called a child station side). The parent station device is called an OLT (Optical Line Terminal). The child station device is called an ONU (Optical Network Unit).

[0003] Furthermore, optical communication systems may employ an FM batch conversion method, for example, as described in Non-Patent Document 1. Here, a technique has been proposed for reducing the gain of an amplifier in accordance with the detection level of an unwanted wave signal (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-205408 [Patent Document 2] Japanese Patent Application Publication No. 7-15718 [Non-patent literature]

[0005] [Non-Patent Document 1] internet<URL:https: / / www.rd.ntt / as / history / access / ac0113.html> Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, an ONU included in an optical communication system that employs an FM batch conversion method demodulates pre-demodulation data (hereinafter referred to as an FM (Frequency Modulation) signal). Demodulation is performed based on parameters. However, if the parameters are not optimal, the demodulated data (hereinafter referred to as a demodulated signal) will not be in an optimal state. Therefore, the problem is how to optimize the demodulated signal.

[0007] The objective of this disclosure is to optimize the demodulated signal. [Means for solving the problem]

[0008] According to one aspect of the present disclosure Demodulator is provided. The demodulator demodulates an FM signal and includes a demodulation unit that demodulates the FM signal based on parameters, and a control unit that, when at least one of the reception power of the FM signal, the internal temperature of the demodulator, the external temperature of the demodulator, the voltage value of a demodulated signal obtained by demodulating the FM signal, and the current value of the demodulated signal fluctuates, identifies the parameter corresponding to the fluctuated value from a setting table and sets the identified parameter in the demodulation unit. [Effects of the Invention]

[0009] According to the present disclosure, the demodulated signal can be optimized. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a comparative example of an optical communication system. [Figure 2] 1 is a diagram illustrating an optical communication system according to a first embodiment. [Figure 3] 2 is a block diagram showing the functions of an ONU according to the first embodiment. FIG. [Figure 4] 10A and 10B are diagrams illustrating an example of a setting table according to the first embodiment. [Figure 5] 10 is a flowchart illustrating an example of processing executed by an ONU according to the first embodiment. [Figure 6] FIG. 10 is a block diagram showing the functions of an ONU according to a second embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of a setting table according to the second embodiment. [Figure 8] 10 is a flowchart illustrating an example of processing executed by an ONU according to the second embodiment. [Figure 9]FIG. 11 is a block diagram showing the functions of an ONU according to a third embodiment. [Figure 10] FIG. 11 is a diagram illustrating an example of a setting table according to the third embodiment. [Figure 11] 11 is a flowchart illustrating an example of processing executed by an ONU according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments are merely examples, and various modifications are possible within the scope of the present disclosure.

[0012] Embodiment 1 1 is a diagram showing a comparative example of an optical communication system, which employs only the FM batch conversion method, and includes an optical line terminal (OLT) 800 and an optical network unit (ONU) 900. The OLT 800 transmits the FM signal to the ONU 900 . The ONU 900 includes a receiving unit 910, a demodulating unit 920, an amplifying unit 930, a detecting unit 940, and a control unit 950. The receiving unit 910 receives an FM signal. The demodulating unit 920 demodulates the FM signal based on parameters. The amplifying unit 930 amplifies the demodulated signal obtained by demodulating the FM signal. The detecting unit 940 detects unwanted waves from the demodulated signal. The control unit 950 reduces the gain of the amplifying unit 930 according to the detection level of the unwanted waves.

[0013] As described above, the demodulator 920 demodulates the FM signal based on the parameters. If the parameters are not optimal, the demodulated signal will not be in an optimal state. Therefore, the question is how to optimize the demodulated signal.

[0014] A method for optimizing the demodulated signal will now be described. FIG. 2 is a diagram illustrating an optical communication system according to a first embodiment. The optical communication system employs an FM batch conversion method. The optical communication system includes an ONU 100 and an OLT 200. The optical communication system may include a communication terminal 300. One ONU is illustrated in FIG. 2. The optical communication system may include two or more ONUs. Also, one OLT is illustrated in FIG. 2. The optical communication system may include two or more OLTs. Furthermore, one communication terminal is illustrated in FIG. 2. The optical communication system may include two or more communication terminals.

[0015] The ONU 100 communicates with the OLT 200 via an optical fiber cable and an optical coupler. The ONU 100 is connected to the communication terminal 300 via a communication line such as a LAN (Local Area Network) cable or a coaxial cable. In Figure 2, the signal flow in the FM batch conversion system is shown by a solid line, and the signal flow in a GE-PON (Gigabit Ethernet-Passive Optical Network) is shown by a dashed line.

[0016] The OLT 200 has a communication processing unit 210. For example, the communication processing unit 210 is realized by an optical module. The communication processing unit 210 transmits an FM signal to the ONU 100. The communication processing unit 210 also transmits and receives signals in the GE-PON. The OLT 200 may have a function to transmit an FM signal to the ONU 100 and a function to transmit and receive signals in the GE-PON separately. Also, either the function to transmit an FM signal to the ONU 100 or the function to transmit and receive signals in the GE-PON may be provided by another OLT.

[0017] The communication terminal 300 is a Home Gateway (HGW) device, a Voice over Internet Protocol (VoIP) device, a Personal Computer (PC), a Television (TV), or the like.

[0018] The communication terminal 300 includes a receiving unit 310 and a communication processing unit 320. For example, the receiving unit 310 is realized by a receiving integrated circuit (IC), a receiving circuit, etc. For example, the communication processing unit 320 is realized by an application specific integrated circuit (ASIC), a large-scale integration (LSI), a memory, etc. As will be described later, the receiving unit 310 receives a signal obtained by amplifying the demodulated signal from the ONU 100. The receiving unit 310 may also receive the demodulated signal. The communication processing unit 320 transmits and receives signals in the GE-PON.

[0019] Next, the functions of the ONU 100 will be described. 3 is a block diagram showing the functions of the ONU according to the embodiment 1. The ONU 100 includes a communication unit 110, a demodulation unit 120, an amplification unit 130, a reception power measurement unit 140, a control unit 150, and a communication processing unit 160.

[0020] For example, the communication unit 110 is realized by an optical module. For example, the demodulation unit 120 is realized by a demodulation IC, a demodulation circuit, or the like. For example, the amplification unit 130 is realized by an AMP (amplifier) ​​IC, an AMP circuit, or the like. For example, the reception power measurement unit 140 is realized by an IC, a processing circuit, or the like. For example, the control unit 150 is realized by an ASIC, an LSI, a memory, or the like. For example, the communication processing unit 160 is realized by an ASIC, an LSI, a memory, or the like.

[0021] The communication unit 110 receives an FM signal (optical signal). Here, the communication unit 110 has an O (Optical) / E (Electrical) conversion function. Therefore, the communication unit 110 converts the FM signal (optical signal) into an FM signal (electrical signal). The FM signal (electrical signal) is input to the demodulation unit 120.

[0022] Furthermore, when the communication unit 110 receives a signal in GE-PON from the OLT 200, it converts the signal into an electrical signal and transmits the converted electrical signal to the communication processing unit 160. When the communication unit 110 receives a signal in GE-PON from the communication processing unit 160, it converts the signal into an optical signal and transmits the converted optical signal to the OLT 200.

[0023] The demodulation unit 120 demodulates the FM signal (electrical signal) based on the parameters, which will be explained later. The amplifier 130 amplifies a demodulated signal obtained by demodulating an FM signal (electrical signal). The amplified signal is transmitted to the communication terminal 300. The amplifier 130 may also have an AC (Alternating Current) / DC (Direct Current) conversion function. The amplifier 130 may also adjust the gain.

[0024] The reception power measuring unit 140 measures the optical power of the FM signal (optical signal) received by the communication unit 110 as reception power. The reception power may also be called a reception level. The reception power measuring unit 140 may measure the reception power constantly or periodically. The control unit 150 stores a setting table. An example of the setting table is shown below.

[0025] 4(A) and (B) are diagrams showing examples of setting tables according to the first embodiment. Setting table 151 is stored in control unit 150. Setting table 151 shows the correspondence between reception power and parameters.

[0026] Here, the demodulation unit 120 may use the detection threshold of the detection pulse, the amplitude of the rising detection pulse, and the amplitude of the falling detection pulse as parameters. Also, the demodulation unit 120 may use arbitrary values ​​as parameters. When the detection threshold of the detection pulse, the amplitude of the rising detection pulse, and the amplitude of the falling detection pulse are used as parameters, the control unit 150 uses the setting table 151 of FIG. 4(A). When arbitrary values ​​are used as parameters, the control unit 150 uses the setting table 151 of FIG. 4(B). In this way, the control unit 150 can select the setting table 151 in accordance with the design of the demodulation unit 120. In the following description, it is assumed that the demodulation unit 120 uses the detection threshold of the detection pulse, the amplitude of the rising detection pulse, and the amplitude of the falling detection pulse as parameters. Therefore, for example, it is assumed that the setting table 151 of FIG. 4(A) is used.

[0027] The control unit 150 specifies parameters according to the measured reception power based on the setting table 151. For example, when the reception power is "reception power 1," the control unit 150 specifies the detection threshold value "th1" of the detection pulse, the amplitude "u1" of the rising detection pulse, and the amplitude "d1" of the falling detection pulse as the parameters. The control unit 150 sets the identified parameters in the demodulation unit 120. As a result, the demodulation unit 120 performs demodulation based on the set parameters. Furthermore, the control unit 150 stores previously measured reception power, for example, the previously measured reception power being the reception power measured just before.

[0028] Returning to FIG. 3, the communication processing unit 160 will be described. When the communication processing unit 160 receives a signal in the GE-PON from the communication unit 110, it transmits the signal to the communication terminal 300. When the communication processing unit 160 receives a signal in the GE-PON from the communication terminal 300, it transmits the signal to the communication unit 110.

[0029] It should be noted that the ONU 100 does not necessarily have to include the amplifier 130. If the ONU 100 does not include the amplifier 130, the demodulated signal may be input to an amplifier. It should be noted that the amplifier exists outside the ONU 100. If the ONU 100 does not include the amplifier 130, the demodulated signal may be input to the communication terminal 300. Furthermore, the ONU 100 does not necessarily have to include the communication processing unit 160.

[0030] Next, the processing executed by the ONU 100 will be explained using a flowchart. FIG. 5 is a flowchart illustrating an example of a process executed by the ONU according to the first embodiment. (Step S11) The communication unit 110 receives an FM signal (optical signal). (Step S12) The reception power measuring unit 140 measures the optical power of the FM signal (optical signal) received by the communication unit 110 as reception power. This reception power is also referred to as the currently measured reception power or the first reception power. In the following description, this reception power is referred to as the currently measured reception power. Note that this reception power may also be referred to as the currently measured reception level.

[0031] (Step S13) The control unit 150 compares the reception power measured in the past with the reception power measured this time. The reception power measured this time may be transmitted by the reception power measurement unit 140 and acquired by the control unit 150. The reception power measured this time may also be obtained by the control unit 150 acquiring it from the reception power measurement unit 140. The control unit 150 determines whether the reception power has fluctuated. If the reception power has fluctuated, the process proceeds to step S14. If the reception power has not fluctuated, the process ends. Note that fluctuating means that a difference has occurred. (Step S14) Based on the setting table 151, the control unit 150 identifies parameters according to the currently measured reception power. (Step S15) The control unit 150 sets the identified parameters in the demodulation unit 120. The ONU 100 repeats steps S11 to S15 while receiving the FM signal (optical signal).

[0032] According to the first embodiment, the ONU 100 identifies optimal parameters according to the currently measured reception power, and demodulates the FM signal (electrical signal) based on the identified parameters. Therefore, the demodulated signal obtained by demodulating the FM signal (electrical signal) is in an optimal state. Therefore, the ONU 100 can optimize the demodulated signal.

[0033] Furthermore, the ONU 100 automatically changes parameters in accordance with changes in the environment. This eliminates the need for the user to change parameters. As a result, the ONU 100 can reduce the workload on the user. Furthermore, the ONU 100 can automatically optimize the demodulated signal without relying on the functions of the devices (e.g., the OLT 200) that make up the optical communication system.

[0034] Embodiment 2 Next, a description will be given of embodiment 2. In embodiment 2, differences from embodiment 1 will be mainly described. Furthermore, in embodiment 2, description of matters common to embodiment 1 will be omitted.

[0035] Fig. 6 is a block diagram showing the functions of the ONU according to embodiment 2. The components in Fig. 6 that are the same as those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3. The ONU 100a includes a control unit 150a and a temperature measurement unit 170. The point that the reception power measurement unit 140 is replaced with the temperature measurement unit 170 is a major difference from the first embodiment.

[0036] For example, the temperature measurement unit 170 is realized by a thermistor, a temperature sensor, or the like. The temperature measurement unit 170 measures the internal temperature of the ONU 100a. If the temperature measurement unit 170 is implemented as a thermistor, the temperature measurement unit 170 can obtain the internal temperature of the ONU 100a by measuring the resistance value. The temperature measurement unit 170 may also transmit measurement information, which is information obtained when the internal temperature of the ONU 100a is measured, to the control unit 150a. Specifically, the measurement information is a voltage value, a current value, or a resistance value obtained when the internal temperature of the ONU 100a is measured. The temperature measurement unit 170 may constantly measure the internal temperature of the ONU 100a, or may periodically measure the internal temperature of the ONU 100a.

[0037] The control unit 150a receives the internal temperature or measurement information of the ONU 100a from the temperature measurement unit 170. The internal temperature or measurement information of the ONU 100a may be obtained by the control unit 150a acquiring it from the temperature measurement unit 170. The control unit 150a may calculate the external temperature of the ONU 100a using the internal temperature or measurement information of the ONU 100a. Specifically, the control unit 150a calculates the external temperature of the ONU 100a using equation (1). Note that a and b are coefficients that depend on the device. Note that the calculation of the external temperature may be performed by a functional unit other than the control unit 150a (for example, the temperature measurement unit 170).

[0038] Internal temperature = a × external temperature + b … (1)

[0039] The control unit 150a stores a setting table, which is exemplified below.

[0040] 7 is a diagram showing an example of a setting table according to the second embodiment. The setting table 151a is stored in the control unit 150a. The setting table 151a shows the correspondence between the measurement information, the internal temperature of the ONU 100a, the external temperature of the ONU 100a, and parameters. The setting table 151a may also show the correspondence between the measurement information, the internal temperature of the ONU 100a, or the external temperature of the ONU 100a, and parameters.

[0041] The control unit 150a identifies parameters corresponding to the measurement information, the internal temperature of the ONU 100a, or the external temperature of the ONU 100a based on the setting table 151a. For example, if the internal temperature is "it1," the control unit 150a identifies the detection threshold value "th1" of the detection pulse, the amplitude "u1" of the rising detection pulse, and the amplitude "d1" of the falling detection pulse as the parameters. The control unit 150a sets the identified parameters in the demodulation unit 120. As a result, the demodulation unit 120 performs demodulation based on the set parameters.

[0042] Furthermore, the control unit 150a stores past measurement information, the internal temperature of the ONU 100a measured in the past (hereinafter referred to as the past internal temperature), or the external temperature of the ONU 100a calculated in the past (hereinafter referred to as the past external temperature). For example, the past measurement information is information on the previous measurement of the internal temperature of the ONU 100a. For example, the past internal temperature is the internal temperature of the ONU 100a measured last time. For example, the past external temperature is the external temperature of the ONU 100a calculated last time.

[0043] Next, the process executed by the ONU 100a will be explained using a flowchart. FIG. 8 is a flowchart illustrating an example of processing executed by the ONU according to the second embodiment. (Step S21) The temperature measurement unit 170 measures the internal temperature of the ONU 100a. This internal temperature is also referred to as the current internal temperature or the first internal temperature. In the following description, this internal temperature is also referred to as the current internal temperature. The temperature measurement unit 170 may also transmit measurement information or the external temperature to the control unit 150a. This measurement information is also referred to as the current measurement information or the first measurement information. This external temperature is also referred to as the current external temperature or the first external temperature. In the following description, this measurement information is also referred to as the current measurement information. This external temperature is also referred to as the current external temperature.

[0044] (Step S22) The control unit 150a receives the current internal temperature from the temperature measurement unit 170. The control unit 150a may receive the current measurement information or the external temperature from the temperature measurement unit 170. The control unit 150a may also calculate the external temperature of the ONU 100a using the current internal temperature or the current measurement information. This external temperature is also referred to as the current external temperature or the first external temperature. In the following description, this external temperature is referred to as the current external temperature.

[0045] (Step S23) The control unit 150a compares the past internal temperature with the current internal temperature. The control unit 150a may compare the past measurement information with the current measurement information. The control unit 150a may compare the past external temperature with the current external temperature. The control unit 150a determines whether a fluctuation has occurred. For example, the control unit 150a determines whether the internal temperature has fluctuated. For example, the control unit 150a determines whether the measurement information has fluctuated. For example, the control unit 150a determines whether the external temperature has fluctuated. If a change has occurred, the process proceeds to step S24. If a change has not occurred, the process ends.

[0046] (Step S24) The control unit 150a identifies parameters corresponding to the current internal temperature based on the setting table 151a. The control unit 150a may identify parameters corresponding to the current measurement information based on the setting table 151a. The control unit 150a may identify parameters corresponding to the current external temperature based on the setting table 151a. (Step S25) The control unit 150a sets the identified parameters in the demodulation unit 120. The ONU 100a repeats steps S21 to S25 while receiving the FM signal (optical signal).

[0047] According to the second embodiment, the ONU 100a identifies optimal parameters according to the current measurement information, the current internal temperature, or the current external temperature, and demodulates the FM signal (electrical signal) based on the identified parameters. Therefore, the demodulated signal obtained by demodulating the FM signal (electrical signal) is in an optimal state. Therefore, the ONU 100a can optimize the demodulated signal.

[0048] Furthermore, the ONU 100a automatically changes the parameters in accordance with changes in the environment. This eliminates the need for the user to change the parameters. Therefore, the ONU 100a can reduce the workload on the user. Furthermore, the ONU 100a can automatically optimize the demodulated signal without relying on the functions of the devices (e.g., the OLT 200) that make up the optical communication system.

[0049] Embodiment 3 Next, a description will be given of embodiment 3. In embodiment 3, differences from embodiment 1 will be mainly described. Furthermore, in embodiment 3, description of matters common to embodiment 1 will be omitted.

[0050] 9 is a block diagram showing the functions of an ONU according to embodiment 3. The components in FIG. 9 that are the same as those shown in FIG. 3 are assigned the same reference numerals as those shown in FIG. The ONU 100b includes a control unit 150b and a measurement unit 180. The reception power measurement unit 140 is replaced with the measurement unit 180, which is a major difference from the first embodiment.

[0051] For example, the measurement unit 180 is realized by an analog-to-digital converter (ADC), a comparator, or the like. The measuring unit 180 measures the voltage value of the demodulated signal. The measurement target of the measuring unit 180 may be, for example, the amplitude of the rising detection pulse and the amplitude of the falling detection pulse. The measuring unit 180 may measure the current value of the signal demodulated by the demodulating unit 120. The measuring unit 180 may perform measurements constantly or periodically.

[0052] The control unit 150b stores a setting table, which is exemplified below.

[0053] 10 is a diagram showing an example of a setting table according to the third embodiment. Setting table 151b is stored in control unit 150b. Setting table 151b shows the correspondence between the voltage value of a demodulated signal, the current value of a demodulated signal, and parameters. Setting table 151b may also show the correspondence between the voltage value of a demodulated signal or the current value of a demodulated signal and parameters.

[0054] For example, voltage value 1 shown in setting table 151b of Fig. 10 may be considered to be the amplitude of a rising detection pulse as a voltage value of a demodulated signal. Also, for example, voltage value 2 shown in setting table 151b of Fig. 10 may be considered to be the amplitude of a falling detection pulse as a voltage value of a demodulated signal. The current value items shown in setting table 151b of Fig. 10 are items that refer to current values ​​measured by measurement unit 180.

[0055] The control unit 150b identifies parameters corresponding to the voltage value or current value measured by the measurement unit 180 based on the setting table 151b. For example, if the current value is "c1", the control unit 150b identifies the following parameters: a detection threshold value "th1" of the detection pulse, an amplitude "u1" of the rising detection pulse, and an amplitude "d1" of the falling detection pulse. The control unit 150b sets the identified parameters in the demodulation unit 120. As a result, the demodulation unit 120 performs demodulation based on the set parameters.

[0056] Furthermore, the control unit 150b stores voltage values ​​of the demodulated signal measured in the past (hereinafter referred to as past voltage values) or current values ​​of the demodulated signal measured in the past (hereinafter referred to as past current values). For example, the past voltage values ​​are voltage values ​​measured last time. For example, the past current values ​​are current values ​​measured last time.

[0057] Next, the process executed by the ONU 100b will be described with reference to a flowchart. FIG. 11 is a flowchart illustrating an example of processing executed by an ONU according to the third embodiment. (Step S31) The measuring unit 180 measures the voltage value of the demodulated signal. This voltage value is also referred to as the current voltage value or the first voltage value. Hereinafter, this voltage value will be referred to as the current voltage value. The measuring unit 180 may measure the current value of the demodulated signal. This current value is also referred to as the current current value or the first current value. Hereinafter, this current value will be referred to as the current current value.

[0058] (Step S32) Control unit 150b receives the current voltage value from measurement unit 180. Control unit 150b may also receive the current current value from measurement unit 180. Furthermore, control unit 150b may obtain the current voltage value or the current current value by acquiring it from measurement unit 180.

[0059] (Step S33) The control unit 150b compares the past voltage value with the current voltage value. The control unit 150b may also compare the past current value with the current current value. The control unit 150b determines whether a fluctuation has occurred. For example, the control unit 150b determines whether a voltage value has fluctuated. For example, the control unit 150b determines whether a current value has fluctuated. If a change has occurred, the process proceeds to step S34. If a change has not occurred, the process ends.

[0060] (Step S34) The control unit 150b identifies parameters corresponding to the current voltage value based on the setting table 151b. The control unit 150b may also identify parameters corresponding to the current current value based on the setting table 151b. (Step S35) The control unit 150b sets the identified parameters in the demodulation unit 120. The ONU 100b repeats steps S31 to S35 while receiving the FM signal (optical signal).

[0061] According to the third embodiment, the ONU 100b identifies optimal parameters according to the current voltage value or the current current value, and demodulates the FM signal (electrical signal) based on the identified parameters. Therefore, the demodulated signal obtained by demodulating the FM signal (electrical signal) is in an optimal state. Therefore, the ONU 100b can optimize the demodulated signal.

[0062] Furthermore, the ONU 100b automatically changes the parameters in accordance with changes in the environment. This eliminates the need for the user to change the parameters. Therefore, the ONU 100b can reduce the workload on the user. Furthermore, the ONU 100b can automatically optimize the demodulated signal without relying on the functions of the devices (e.g., the OLT 200) that make up the optical communication system.

[0063] The first to third embodiments have been described as being applied to an optical communication system that employs an FM batch conversion method. However, the first to third embodiments may also be applied to a wireless communication system or a wired communication system that includes a demodulator that demodulates an FM signal.

[0064] The features of the above-described embodiments can be combined with each other as appropriate. For example, the first and second embodiments may be combined. For example, the ONU 100 includes a communication unit 110, a reception power measurement unit 140, a temperature measurement unit 170, a demodulation unit 120, and a control unit 150. The communication unit 110 receives an optical signal, which is an FM signal. The reception power measurement unit 140 measures the optical power of the optical signal as a first reception power. The temperature measurement unit 170 measures a first internal temperature, which is the internal temperature of the ONU 100. The demodulation unit 120 demodulates the electrical signal converted from the optical signal based on the parameters. The control unit 150 stores a setting table indicating the correspondence between the reception power, the internal temperature of the ONU 100, or measurement information, which is information when the internal temperature is measured, or the external temperature of the ONU 100, and the parameters. The control unit 150 stores the reception power measured in the past, the internal temperature measured in the past, the measurement information, or the external temperature calculated in the past. When a difference occurs between the previously measured receiving power and the first receiving power, and a difference occurs between the previously measured internal temperature and the first internal temperature, or a difference occurs between the first measurement information, which is the information when the first internal temperature is measured, and the previously measured information, or a difference occurs between the first external temperature calculated based on the first internal temperature and the previously calculated external temperature, the control unit 150 identifies parameters corresponding to the first receiving power and the first internal temperature, or the first measurement information, or the first external temperature based on the setting table, and sets the identified parameters in the demodulation unit 120.

[0065] Also, for example, the first and third embodiments may be combined. For example, the ONU 100 includes a communication unit 110, a reception power measurement unit 140, a demodulation unit 120, a measurement unit 180, and a control unit 150. The communication unit 110 receives an optical signal that is an FM signal. The reception power measurement unit 140 measures the optical power of the optical signal as a first reception power. The demodulation unit 120 demodulates the electrical signal converted from the optical signal based on parameters. The measurement unit 180 measures a first voltage value that is the voltage value of the demodulated signal or a first current value that is the current value of the demodulated signal. The control unit 150 stores a setting table indicating the correspondence between the reception power, the voltage value of the demodulated signal or the current value of the demodulated signal, and the parameters. The control unit 150 stores previously measured reception power, and previously measured voltage values ​​of the demodulated signal or previously measured current values ​​of the demodulated signal. When a difference occurs between the previously measured received power and the first received power, and when a difference occurs between the previously measured voltage value of the demodulated signal and the first voltage value, or when a difference occurs between the previously measured voltage value of the demodulated signal and the first current value, the control unit 150 identifies parameters corresponding to the first received power and the first voltage value or the first current value based on the setting table, and sets the identified parameters in the demodulation unit 120.

[0066] Furthermore, for example, the second embodiment and the third embodiment may be combined. For example, the ONU 100 includes a communication unit 110, a temperature measurement unit 170, a demodulation unit 120, a measurement unit 180, and a control unit 150. The communication unit 110 receives an optical signal, which is an FM signal. The temperature measurement unit 170 measures a first internal temperature, which is the internal temperature of the ONU 100. The demodulation unit 120 demodulates an electrical signal converted from the optical signal based on parameters. The measurement unit 180 measures a first voltage value, which is the voltage value of the demodulated signal, or a first current value, which is the current value of the demodulated signal. The control unit 150 stores the internal temperature of the ONU 100, measurement information, which is information when the internal temperature is measured, or a setting table indicating the correspondence between the external temperature of the ONU 100, the voltage value of the demodulated signal, or the current value of the demodulated signal, and parameters. The control unit 150 stores a previously measured internal temperature, or previously measured measurement information, or a previously calculated external temperature, and a previously measured voltage value of the demodulated signal, or a previously measured current value of the demodulated signal. When a difference occurs between the previously measured internal temperature and a first internal temperature, or a difference occurs between first measurement information, which is information when the first internal temperature is measured, and the previously measured measurement information, or a difference occurs between a first external temperature calculated based on the first internal temperature and a previously calculated external temperature, and a difference occurs between a previously measured voltage value of the demodulated signal and the first voltage value, or a difference occurs between a previously measured voltage value of the demodulated signal and the first current value, the control unit 150 identifies parameters corresponding to the first internal temperature, or the first measurement information, or the first external temperature, and the first voltage value or the first current value, based on the setting table, and sets the identified parameters in the demodulation unit 120.

[0067] Furthermore, for example, the first, second, and third embodiments may be combined. For example, the ONU 100 includes a communication unit 110, a received power measurement unit 140, a temperature measurement unit 170, a demodulation unit 120, a measurement unit 180, and a control unit 150. The communication unit 110 receives an optical signal that is an FM signal. The received power measurement unit 140 measures the optical power of the optical signal as a first received power. The temperature measurement unit 170 measures a first internal temperature that is the internal temperature of the ONU 100. The demodulation unit 120 demodulates the electrical signal converted from the optical signal based on parameters. The measurement unit 180 measures a first voltage value that is the voltage value of the demodulated signal, or a first current value that is the current value of the demodulated signal. The control unit 150 stores a setting table indicating the correspondence between the reception power, the internal temperature of the ONU 100, or measurement information that is information when the internal temperature is measured, or the external temperature of the ONU 100, the voltage value of the demodulated signal, or the current value of the demodulated signal, and parameters. The control unit 150 stores the reception power measured in the past, the internal temperature measured in the past, or the measurement information, or the external temperature calculated in the past, and the voltage value of the demodulated signal measured in the past or the current value of the demodulated signal measured in the past. When a difference occurs between the previously measured receiving power and the first receiving power, and a difference occurs between the previously measured internal temperature and the first internal temperature, or a difference occurs between the first measurement information, which is the information when the first internal temperature is measured, and the previously measured measurement information, or a difference occurs between the first external temperature calculated based on the first internal temperature and the previously calculated external temperature, and a difference occurs between the previously measured voltage value of the demodulated signal and the first voltage value, or a difference occurs between the previously measured voltage value of the demodulated signal and the first current value, the control unit 150 identifies parameters corresponding to the first receiving power, the first internal temperature, or the first measurement information, or the first external temperature, and the first voltage value or the first current value based on the setting table, and sets the identified parameters in the demodulation unit 120. [Explanation of symbols]

[0068] 110 communication unit, 120 demodulation unit, 130 amplification unit, 140 reception power measurement unit, 150 control unit, 150a control unit, 150b control unit, 151 setting table, 151a setting table, 151b setting table, 160 communication processing unit, 170 temperature measurement unit, 180 measurement unit, 210 communication processing unit, 300 communication terminal, 310 receiving unit, 320 communication processing unit, 910 receiving unit, 920 demodulation unit, 930 amplification unit, 940 detection unit, 950 control unit.

Claims

1. 1. A demodulator for demodulating an FM signal, comprising: A demodulator comprising: a demodulator unit that demodulates the FM signal based on parameters; and a control unit that, when at least one of the received power of the FM signal, the internal temperature of the demodulator, the external temperature of the demodulator, the voltage value of the demodulated signal obtained by demodulating the FM signal, and the current value of the demodulated signal fluctuates, identifies the parameter corresponding to the fluctuated value from a setting table and sets the identified parameter in the demodulator unit.

2. 2. The demodulator according to claim 1, wherein the demodulator demodulates the signal using a detection threshold value for the detection pulse, an amplitude of the rising detection pulse, and an amplitude of the falling detection pulse as the parameters.

3. 3. An optical communication device comprising the demodulator according to claim 1 or 2, which is a slave station device included in an optical communication system employing an FM batch conversion method, an optical communication device including a communication unit that receives the optical signal, which is an FM signal, and wherein the demodulation unit demodulates the electrical signal into which the optical signal, which is the FM signal, is converted;

4. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a reception power measuring unit that measures the optical power of the optical signal as a first reception power; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a control unit that stores a setting table indicating a correspondence relationship between reception power and parameters and reception power measured in the past, compares the previously measured reception power with the first reception power, and, when the reception power fluctuates, identifies a parameter corresponding to the first reception power based on the setting table, and sets the identified parameter in the demodulation unit; An optical communication device having:

5. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a temperature measurement unit that measures a first internal temperature that is an internal temperature of the optical communication device; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a control unit that stores a setting table indicating a correspondence between an internal temperature of the optical communication device and a parameter, and an internal temperature of the optical communication device that has been measured in the past, compares the internal temperature that has been measured in the past with the first internal temperature, and, if the internal temperature fluctuates, identifies a parameter corresponding to the first internal temperature based on the setting table, and sets the identified parameter in the demodulation unit; An optical communication device having:

6. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a temperature measurement unit that measures a first internal temperature that is an internal temperature of the optical communication device; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a control unit that stores a setting table indicating a correspondence between measurement information, which is information when an internal temperature of the optical communication device, and parameters, and the past measurement information, receives first measurement information, which is information when the first internal temperature is measured, compares the past measurement information with the first measurement information, and, when the measurement information varies, identifies a parameter corresponding to the first measurement information based on the setting table, and sets the identified parameter in the demodulation unit; An optical communication device having:

7. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a temperature measurement unit that measures a first internal temperature that is an internal temperature of the optical communication device; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a control unit that stores a setting table indicating a correspondence between an external temperature of the optical communication device and a parameter, and past external temperatures, calculates a first external temperature that is the external temperature of the optical communication device using the first internal temperature, compares the past external temperature with the first external temperature, and, when the external temperature fluctuates, identifies a parameter corresponding to the first external temperature based on the setting table, and sets the identified parameter in the demodulation unit; An optical communication device having:

8. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a measurement unit that measures a first voltage value that is a voltage value of a demodulated signal obtained by demodulating the electrical signal; a control unit that stores a setting table indicating a correspondence between a voltage value of the demodulated signal and a parameter and previously measured voltage values ​​of the demodulated signal, compares the previously measured voltage value of the demodulated signal with the first voltage value, and, when the voltage value of the demodulated signal fluctuates, identifies a parameter corresponding to the first voltage value based on the setting table and sets the identified parameter in the demodulation unit; An optical communication device having:

9. An optical communication device that is a slave station device included in an optical communication system that employs an FM batch conversion method, a communication unit that receives an optical signal that is an FM signal; a demodulation unit that demodulates the electrical signal converted from the optical signal based on parameters; a measurement unit that measures a first current value that is a current value of a demodulated signal obtained by demodulating the electrical signal; a control unit that stores a setting table indicating a correspondence between a current value of the demodulated signal and a parameter and a current value of the demodulated signal measured in the past, compares the current value of the demodulated signal measured in the past with the first current value, and, when the current value of the demodulated signal fluctuates, identifies a parameter corresponding to the first current value based on the setting table, and sets the identified parameter in the demodulation unit; An optical communication device having:

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