Temperature estimation device and temperature estimation method

Abstract

In the present invention, an estimation unit of a temperature estimation device detects, from the spectrum of an optical signal transmitted through an optical transmission line on which are formed one or more wavelength filters for filtering and transmitting the wavelength regions of portions of inputted light and filtering wavelength regions each having a different center wavelength, the oscillation peak wavelength of a laser used to generate the optical signal and the filtering center wavelengths of the respective wavelength filters, estimates, on the basis of the detected oscillation peak wavelength, the temperature of the device that generated the optical signal, and estimates the temperature of the surroundings of the wavelength filters on the basis of the detected center wavelengths.

Description

Temperature Estimation Device and Temperature Estimation Method

[0001] The present invention relates to a temperature estimation device and a temperature estimation method.

[0002] For disaster prevention and wildlife control, environmental data sensing by an IoT (Internet of Things) gateway (IoT-GW) is required. For example, sensing data is acquired by a wired or wireless IoT sensor, and the IoT-GW performs data processing on the sensing data and transmits it to the OLT side. In order to operate under the constraint of limited power by optical power supply in a non-electrified area, power saving of the IoT-GW is necessary. Therefore, there is a technology for power saving of the IoT-GW (see, for example, Non-Patent Document 1).

[0003] Also, as a general temperature acquisition method, there is a method of estimating temperature based on the reflection spectrum of a "reflective" fiber Bragg grating (FBG).

[0004] R. Miyatake, H. Katsurai, Y. Fukada, M. Sekiguchi and T. Yoshida, "Ultra-Low-Power Optical Network Unit Driven by Optical Power Supply Using Single-Mode Fiber", IEEE Photonics Technology Letters, vol. 35, no. 16, pp. 874-877, Aug. 2023

[0005] For example, in the use case of environmental data sensing in agriculture, monitoring and controlling the surface temperature of cultivated land is useful for stable crop growth. However, when the number of IoT temperature sensors is increased, problems such as an increase in data volume and power, and coverage limitation of the IoT sensing area occur. Also, when monitoring the state of the IoT-GW itself at the same time, it is important to grasp the temperature inside the housing. However, in the prior art, temperature measurement by an IoT temperature sensor is common. Therefore, it is required to simultaneously acquire the temperature of the IoT-GW and the external environmental temperature while reducing the number of sensors for power saving of the IoT-GW.

[0006] In view of the above circumstances, the present invention aims to provide a temperature estimation device and a temperature estimation method that can estimate the temperature inside and outside a device with low power consumption.

[0007] One aspect of the present invention is a temperature estimation device comprising: a wavelength filter that filters and transmits a portion of the wavelength range of input light, wherein one or more of the wavelength filters, each filtering wavelength range with a different center wavelength, are formed on an optical transmission path, and the estimation unit detects the oscillation peak wavelength of the laser used to generate the optical signal and the center wavelength of the filling of each of the wavelength filters from the spectrum of the optical signal transmitted through the optical transmission path, estimates the temperature of the device that generated the optical signal based on the detected oscillation peak wavelength, and estimates the temperature around the wavelength filter based on the detected center wavelength.

[0008] One aspect of the present invention is a temperature estimation method comprising the steps of: detecting the oscillation peak wavelength of a laser used to generate the optical signal and the center wavelength of the filling of each of the wavelength filters from the spectrum of an optical signal transmitted through an optical transmission path in which one or more of the wavelength filters are formed, each filtering wavelength ranges with different center wavelengths; estimating the temperature of the device that generated the optical signal based on the detected oscillation peak wavelength; and estimating the temperature around the wavelength filter based on the detected center wavelength.

[0009] This invention makes it possible to estimate the temperature inside and outside the device with low power consumption.

[0010] This figure shows the overview configuration of a data acquisition system according to one embodiment of the present invention. This figure shows the spectrum of an optical signal according to the same embodiment. This figure shows an example configuration of a data acquisition system according to the first embodiment. This figure shows the shift of the peak wavelength and Bragg wavelength according to the same embodiment. This is a flowchart showing the operation of the data acquisition system according to the first embodiment. This figure shows an example configuration of a data acquisition system according to the second embodiment. This figure shows the spectra of an optical signal and a reference signal according to the second embodiment. This figure shows the MCF according to the second embodiment. This figure shows the transmission characteristics of the FBG used in the third embodiment and the spectrum after transmission through the FBG. This figure shows an example hardware configuration of a control device according to the first to third embodiments.

[0011] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a diagram showing the schematic configuration of a data acquisition system according to one embodiment of the present invention. Figure 1 shows the upstream configuration. The data acquisition system includes an IoT-GW 10, an OLT 20, a single-mode fiber (SMF) 30, an optical switch 50, a spectrum analyzer 60, and a control device 70. The direction from IoT-GW 10 to OLT 20 is upstream, and the direction from OLT 20 to IoT-GW 10 is downstream.

[0012] The IoT-GW10 has a transceiver (TRx)11. TRx11 has an LD (laser diode)12 and transmits and receives optical signals. The OLT20 has a TRx21. TRx21 transmits and receives optical signals. The SMF30 is an optical transmission path connecting the IoT-GW10 and the OLT20. TRx11 of the IoT-GW10 outputs an uplink optical signal to the SMF30, which is generated by modulating the light output by LD12 with the transmission data. TRx21 of the OLT20 receives the uplink optical signal output from TRx11 and transmitted through the SMF30.

[0013] Inside the core of the SMF30, N fiber Bragg gratings (FBGs) 40-1 to 40-N (where N is an integer greater than or equal to 1) are formed. Figure 1 shows an example where N = 12. FBG40-1 to 40-N are collectively referred to as FBG40. FBG40 is a transmissive type FBG. FBG40-1 to 40-N are each formed at different locations within the temperature measurement target area R where the SMF30 is laid planarly. FBG40 filters the optical signal output from TRx11 by reflecting a predetermined wavelength band, allowing other wavelength bands to pass through. Each of FBG40-1 to 40-N filters a different central wavelength band. Specifically, FBG40-n (where n is an integer between 1 and N) filters the Bragg wavelength λ ｎ，Ｂｒａｇｇ = 2neffΛ ｎ It reflects light of one wavelength and transmits light of other wavelengths. neff is the effective refractive index, Λ ｎ is the spacing of the diffraction gratings of FBG40-n, and Λ １ ~Λ ｎ These are all different. However, the diffraction grating length, pitch, and diffraction grating coupling constant of FBG40-1 to 40-N are the same.

[0014] An optical switch 50 is inserted between the FBG 40 and TRx 21 of the SMF 30. The optical switch 50 is transmitted by the IoT-GW 10 and switches the output destination of the upstream optical signal that has passed through the FBG 40-1 to 40-N of the SMF 30, to either the OLT 20 or the spectrum analyzer 60. Alternatively, an optical coupler may be provided instead of the optical switch 50. The optical coupler branches a portion of the optical signal transmitted through the SMF 30 and outputs it to the spectrum analyzer 60. The spectrum analyzer 60 detects the spectrum showing the power of each wavelength of the optical signal input from the optical switch 50.

[0015] The control device 70 is connected to the OLT 20 and the spectrum analyzer 60. Based on the spectral information detected by the spectrum analyzer 60, the control device 70 estimates the temperature inside the housing of the IoT-GW 10 and the temperature near each FBG 40 located outside the housing of the IoT-GW 10.

[0016] Figure 2 is a diagram showing the spectrum of an optical signal. Fig. 2(a) shows the spectrum of the optical signal at point A1 shown in Fig. 1. Point A1 is between TRx11 and the first FBG40. The spectrum of the optical signal at point A1 shows the oscillation spectrum of LD12 possessed by TRx11. The peak wavelength of the oscillation spectrum of LD12 is λ ＬＤ is.

[0017] Fig. 2(b) shows the transmission spectra B1 to B12 of each FBG40-1 to 40-12. FBG40 filters a part of the wavelength range of the LD sideband and transmits other wavelengths. The Bragg wavelength λ １ to λ １２ which are the center wavelengths of the wavelength bands filtered by each FBG40-1 to 40-12 are different from each other, and λ １ < λ ２ <... < λ １２ is.

[0018] Fig. 2(c) shows the spectrum of the optical signal at point A2 shown in Fig. 1 that has passed through all the FBG40s. The spectrum of the optical signal at point A2 is detected by the spectrum analyzer 60. Symbol C is the monitoring result of the peak wavelength of LD23, and symbols D1 to D12 are the monitoring results of the dips that appear when the optical signal passes through each FBG40. The wavelength of the dip rides on the sideband of the light output by LD12. The spectrum shown in Fig. 2(c) corresponds to the multiplication of the spectrum shown in Fig. 2(a) and the transmission spectra of each FPG shown in Fig. 2(b).

[0019] As shown in Fig. 1, one or more FBG40s are connected outside the IoT-GW10. Due to the transmission characteristics of FBG40, as shown in Fig. 2(c), apart from the oscillation peak of LD12 of TRx11, an additional distinguishable dip structure appears in the spectrum of the upstream optical signal. For a temperature change dT, the displacement dλ ＬＤ of the oscillation peak wavelength λ of LD12 ＬＤ and the displacement dλ ＦＢＧ of the dip structure by each FBG40 are different. The displacement dλ <00000​​This is determined by the thermo-optic coefficient and the amount of thermal strain. Therefore, the displacement dλ of each output light from LD12 with respect to temperature change is ＬＤ / dT and the displacement dλ of each dip structure Dn of each FBG40-n with respect to temperature change. ＦＢＧ The displacement dλ / dT is estimated in advance by actual measurement or theoretically. The control device 70 then uses the previously obtained displacement dλ ＬＤ Estimate of / dT and displacement dλ of each FBG40 ＦＢＧ Estimate of / dT and the wavelength λ of the peak of the measured data obtained with the spectrum analyzer 60 ＬＤ and the wavelength λ of each dip structure Dn ＦＢＧ By comparing these, it is possible to simultaneously estimate the temperature inside the IoT-GW10 enclosure and the surface temperature of the temperature measurement target area R outside the IoT-GW10 enclosure. The wavelength λ at which the dip structure Dn appears. ＦＢＧ is the Bragg wavelength λ ｎ，Ｂｒａｇｇ It corresponds to this.

[0020] For example, a spectrum analyzer 60 is placed near the OLT 20. The control device 70 is triggered when the TRx21 of the OLT 20 receives an uplink signal from the TRx11 of the IoT-GW 10 for data communication, and drives the spectrum analyzer 60 to acquire the spectrum of the optical signal that has passed through each FBG 40 of the SMF 30. Based on the wavelength of the oscillation peak and the wavelength at which a dip structure appears shown in the spectrum obtained by the spectrum analyzer 60 measuring the optical signal, the control device 70 estimates the temperature inside the housing of the IoT-GW 10 and the surface temperature of the temperature measurement target area R outside the housing.

[0021] According to this embodiment, an IoT temperature sensor for temperature acquisition becomes unnecessary. Therefore, the power consumption on the IoT-GW side required for sensor operation and data communication can be reduced. Furthermore, the light intensity of the light supplied to the IoT-GW can be reduced. In addition, since it becomes possible to monitor the temperature of the light-powered IoT-GW itself and acquire the area temperature around the IoT-GW, the use cases in agriculture and other fields are expanded. Detailed embodiments are described below.

[0022] (First Embodiment) In the first embodiment, optical power is supplied to the IoT-GW from a light source on the station side.

[0023] Figure 3 shows the configuration of the data acquisition system according to the first embodiment. In Figure 3, the same reference numerals are used for parts that are the same as those shown in Figure 1, and their descriptions are omitted. A light source 80, an OLT 20, an optical switch 50, a spectrum analyzer 60, and a control device 70 are installed in the station building. The IoT-GW100 is connected to the light source 80 by an SMF 81 and to the OLT 20 via an SMF 30 through an optical switch 50. The light source 80 may also be provided in the OLT 20. Note that a multicore fiber (MCF) can be used to bundle the uplink SMF 30 and the downlink SMF 81 into a single fiber.

[0024] The IoT-GW100 comprises a photoelectric conversion unit 13, a control unit 14, a communication unit 15, and a TRx 11. The photoelectric conversion unit 13 converts light received from the light source 80 via the SMF 81 into electricity. The photoelectric conversion unit 13 supplies the obtained electricity to the control unit 14, the communication unit 15, and the TRx 11. The control unit 14, the communication unit 15, and the TRx 11 operate using the electricity supplied from the photoelectric conversion unit 13. The control unit 14 controls each of these units. The communication unit 15 acquires sensor data from IoT sensors 82, etc., wirelessly or via wired connection. The control unit 14 processes the sensor data acquired by the communication unit 15 and instructs the TRx 11 to transmit the resulting transmission data. The TRx 11 modulates the light output from the LD 12 using the transmission data instructed by the control unit 14 to generate an uplink optical signal. TRx11 outputs the generated uplink optical signal to SMF30 and transmits it to the station building. TRx11 also receives the downlink optical signal output by TRx21 of OLT20 and transmitted through SMF30.

[0025] FBG40-1 to 40-12 are formed in the core of the SMF30 in the transmission section between TRx11 and TRx21. The transmission spectra of each FBG40-1 to 40-12 are superimposed on the LD oscillation spectrum of the uplink optical signal transmitted from TRx11. The pitch Λ of each diffraction grating of FBG40-1 to 40-12. １ ~Λ １２ Because they differ, the dips in the transmission spectra of each FBG 40-1 to 40-12 can be discriminated.

[0026] The optical switch 50 switches the optical path on the station side. That is, the optical switch 50 switches whether the output destination of the optical signal transmitted through the SMF 30 is TRx 50 or the spectrum analyzer 60. Alternatively, the optical coupler may tap a portion of the optical signal transmitted through the SMF 30 and output it to the spectrum analyzer 60. The spectrum analyzer 60 measures the spectrum of the optical signal received from the optical switch 50 or the optical coupler.

[0027] The control device 70 includes an information acquisition unit 71 and an estimation unit 72. The information acquisition unit 71 acquires information of the signal spectrum measured by the spectrum analyzer 60. The estimation unit 72 estimates the peak wavelength λ of the signal spectrum. ＬＤ Based on this, the relative temperature change or absolute temperature inside the IoT-GW100 enclosure is estimated. Furthermore, the estimation unit 72 uses the wavelength λ of the dip structure appearing in the signal spectrum. １ ~λ １２ Based on this, the relative temperature change or absolute temperature around each of FBG40-1 to 40-12 is estimated.

[0028] Furthermore, by transmitting downstream light from the TRx21 of the OLT20 installed on the station building side to the FBG40 via the SMF30, and performing the same spectral analysis on the reflected light as described above, it is also possible to estimate the relative temperature change or absolute temperature around each FBG40.

[0029] Figure 4 shows the shifts in peak wavelength and Bragg wavelength due to temperature changes. Figure 4(a) shows the LD12 of TRx11 and two FBG40-1 and FBG40-2 formed in SMF30. Figure 4(b) shows the spectrum after the light output from LD12 has passed through FBG40-1 and FBG40-2 shown in Figure 4(a).

[0030] When the temperature is T, the peak wavelength of the oscillation spectrum of LD12 is λ. ＬＤ，Ｔ , the Bragg wavelength of FBG40-1 is λ ＦＢＧ１，Ｔ , the Bragg wavelength of FBG40-2 is λ ＦＢＧ２，Ｔ Figure 4(c) shows the temperature T and the peak wavelength λ of the LD12 oscillation spectrum. ＬＤ，Ｔ Correlation E ＬＤ, temperature T and Bragg wavelength λ ＦＢＧ１，Ｔ Correlation E １ , and temperature T and Bragg wavelength λ ＦＢＧ２，Ｔ Correlation E ２ This indicates.

[0031] Correlation E ＬＤ Correlation E １ Correlation E ２ As shown, with increasing temperature, the peak wavelength λ ＬＤ，Ｔ , Bragg wavelength λ ＦＢＧ１，Ｔ , and Bragg wavelength λ ＦＢＧ２，Ｔ These shift independently. Therefore, based on experiments and theoretical predictions, the peak wavelength λ in the oscillation spectrum of LD12 is determined to be as shown in Figure 4(c). ＬＤ，Ｔ , Bragg wavelength λ of FBG40-1 ＦＢＧ１，Ｔ , and the Bragg wavelength λ of FBG40-2 ＦＢＧ２，Ｔ The temperature dependence of each temperature T is correlated with E. ＬＤ , E １ , E ２ Keep it as is.

[0032] The temperature of the enclosure when the optical signal spectrum was measured is T. ０ The ambient temperature of FBG40-1 is T １ The ambient temperature of FBG40-2 is T ２ The control device 70 determines the peak wavelength λ of LD12 from the spectral measurement results obtained by the spectral analyzer 60. ＬＤ，Ｔ０ , Bragg wavelength λ ＦＢＧ１，Ｔ１ , and Bragg wavelength λ ＦＢＧ２，Ｔ２ The control device 70 detects the previously obtained correlation E ＬＤ From this, the detected peak wavelength λ ＬＤ，Ｔ０ Temperature T corresponding to ０ Similarly, the control device 70 obtains the previously obtained correlation E １ Based on this, the detected Bragg wavelength λ ＦＢＧ１，Ｔ１ Temperature T corresponding to １ Obtain the previously obtained correlation E ２ Based on this, the detected Bragg wavelength λ ＦＢＧ２，Ｔ２ Temperature T corresponding to ２ To obtain.

[0033] In this embodiment, in a certain temperature interval ΔT of interest, the detuning is appropriately set as follows so that each peak can be distinguished and no overtaking due to redshift occurs. Specifically, it is set to satisfy the following equations (1) and (2).

[0034] Δλ ＬＤ <Δλ ＬＤ－ＦＢＧ (1)

[0035] Δλ ＦＢＧ <Δλ ＦＢＧ－ＦＢＧ (2)

[0036] Δλ ＬＤ This is the peak wavelength λ of LD12 when the temperature changes by ΔT. ＬＤ This is the amount of shift (change) of Δλ. ＦＢＧ This is the Bragg wavelength λ of FBG40 when the temperature changes by ΔT. ＦＢＧ This is the amount of shift (change) of Δλ. ＦＢＧ－ＦＢＧ This is the Bragg wavelength λ of FBG40 at the same temperature. ＦＢＧ and other Bragg wavelengths λ of FBG40 ＦＢＧ This is the difference. If the above equations (1) and (2) are satisfied, and the ASE (amplified spontaneous emission) portion from LD12 exceeds the lower limit of measurement of the spectrum analyzer 60, the number of FBG40 can be increased and arranged in the spatial and wavelength domains. Note that Δλ ＦＢＧ－ＦＢＧ Regarding this, it is necessary to set an appropriate value to prevent multiple reflections from occurring between different FBG40s. Basically, the value should be set so that the reflection spectra do not overlap in the wavelength range.

[0037] Figure 5 is a flowchart showing the operation of the data acquisition system. When the IoT-GW100 finishes its periodic sleep, the communication unit 15 receives sensor data from the IoT sensor 82 (step S1). The control unit 14 performs predetermined data processing on the received sensor data to generate transmission data. To send the data to the station, the control unit 14 activates the TRx11. When the TRx11 is activated, the LD12 lights up. The TRx11 modulates the output light from the LD12 with the transmission data to generate an uplink optical signal, which is then output to the SMF30 (step S2).

[0038] The optical switch 50 outputs the optical signal transmitted through the SMF 30 to the OLT 20. The TRx 21 of the OLT 20 receives the optical signal. The OLT 20 uses this reception of the optical signal as a trigger signal for spectrum measurement. That is, the OLT 20 instructs the control device 70 to start the measurement, and the information acquisition unit 71 of the control device 70 sets the optical switch 50 to output the optical signal to the spectrum analyzer 60. Furthermore, the information acquisition unit 71 sets the spectrum analyzer 60 to perform a sweep after the time required for processing in the next steps S4 to S6. The information acquisition unit 71 enters a sweep standby state for the spectrum analyzer. Meanwhile, the control unit 14 of the IoT-GW 100 extinguishes the LD 12 of TRx 11 and enters a sleep state until it receives the instruction for the next cycle (step S3). When the sleep period ends, the control unit 14 of the IoT-GW100 enters a state of waiting to receive sleep information for the next period (step S4).

[0039] When the next cycle begins, TRx21 of OLT20 transmits period sleep information to IoT-GW100. When IoT-GW100 receives period sleep information from OLT20, it activates TRx11 (step S5). TRx11 causes LD12 to emit light and outputs an optical signal to SMF30 (step S6). The optical switch 50 outputs the optical signal transmitted through SMF30 to the spectrum analyzer 60.

[0040] The spectrum analyzer 60 starts sweeping in response to the trigger signal, enabling spectrum measurement. The spectrum analyzer 60 outputs the spectrum of the optical signal input from the optical switch 50 to the control device 70. The information acquisition unit 71 of the control device 70 receives the spectrum of the optical signal. The estimation unit 72 estimates the temperature inside the housing of the IoT-GW100 and the temperature around each FBG 40 based on the wavelengths of the peaks and dip structures shown in the spectrum of the optical signal acquired by the information acquisition unit 71 (step S7).

[0041] In the case of a modulated spectrum, there is a concern that the spectral structure of FBG40 may be difficult to observe due to the modulation sidebands; therefore, LD12 may be made to emit light in CW (Continuous Wave) mode. TRx11 transmits the uplink optical signal, including the CW frame.

[0042] When the estimation unit 72 of the control device 70 finishes estimating the temperature, the information acquisition unit 71 instructs the optical switch 50 to output the optical signal to the OLT 20 and stops the spectrum analyzer 60 (step S8). The IoT-GW 100 enters a period-long sleep state (step S9). The data acquisition system repeats the process from step S1.

[0043] (Second Embodiment) In the first embodiment, one SMF was laid in the temperature measurement area, but in the second embodiment, multiple SMFs are used to increase the number of temperature measurement points, etc. It is also possible to simplify the system using MCF. The second embodiment will be described below, focusing on the differences from the first embodiment.

[0044] Figure 6 shows an example of the upstream configuration of a data acquisition system when multiple SMFs are used. In Figure 6, the same reference numerals are used for parts that are the same as those in the data acquisition system of the first embodiment shown in Figure 3, and their descriptions are omitted.

[0045] TRx11 of the IoT-GW100 transmits and receives optical signals with the personal computer (PC) 22. TRx11 is connected via optical coupler 31 and SMF30-1. PC22, acting as TRx21, is connected via optical coupler 32 and SMF30-2.

[0046] Optical coupler 31 and optical coupler 32 are connected by multiple SMF33-1 to 33-M (where M is an integer greater than or equal to 2). Figure 6 shows the case where M = 4. Each core of SMF33-k (where k is an integer greater than or equal to 1 or greater (M-1)) contains N ｋ pieces (N ｋ FBG40-k-1 to 40-k-N (where is an integer greater than or equal to 1) ｋ A structure is formed. In Figure 5, N １ , N ２ , N ３ This shows the case of 3. On the other hand, no FBG is formed on SMF33-M. Optical coupler 32 and FBG40-k-N on SMF33-k ｋ An optical coupler 34-k is inserted between them. An optical coupler 34-M is also inserted on the SMF 33-M. Optical couplers 34-1 to 34-M are connected to the optical switch 51. Optical couplers 34-1 to 34-M are, for example, 10:1 couplers.

[0047] With the above configuration, TRx11 outputs an optical signal to SMF31. Optical coupler 31 splits the optical signal output from TRx11 and transmitted through SMF31-1 into four and outputs them to SMF33-1 to 33-4. The optical signal transmitted through SMF33-k is referred to as optical signal #k, and the optical signal transmitted through SMF33-M is referred to as the reference signal. The optical signal #k transmitted through SMF33-k has an LD oscillation spectrum that includes each FBG40-k-1 to 40-k-N formed in SMF33-k. ｋ The transmission spectra are superimposed. Each FBG40-k-1 to 40-k-N formed in SMF33-k ｋ Because the pitch of each diffraction grating is different, each FBG40-k-1 to 40-k-N ｋ The dip in the transmission spectrum is discriminable.

[0048] Optical coupler 34-m branches off a portion of the optical signal transmitted through SMF 33-m and outputs it to optical switch 51, while outputting the remaining optical signal to optical coupler 32. Optical coupler 32 superimposes the optical signals input from SMF 33-1 to 33-M and outputs it to SMF 30-2. PC 22 receives the optical signal output from optical coupler 32.

[0049] The optical switch 51 switches whether to output the optical signals #1 to #3 and the reference signal input from each of the optical couplers 34-1 to 34-M to the spectrum analyzer 60. The spectrum analyzer 60 measures the spectra of the optical signals #1 to #3 and the reference signal input from the optical switch 51, and outputs the measurement results to the control device 70.

[0050] The information acquisition unit 71 of the control device 70 acquires information on the spectra of the optical signals #1 to #3 and the reference signal. The estimation unit 72 performs data processing on the spectrum of the optical signal #k using the spectrum of the reference signal. FIG. 7 is a diagram showing the optical signal #k and the reference signal. FIG. 7(a) shows the spectrum W1 of the optical signal #k and the spectrum W2 of the reference signal. The spectrum W2 shows the spectrum of the LD22 alone. FIG. 7(b) shows the transmittance of the optical signal #k after data processing using the reference signal.

[0051] For example, if the estimation unit 72 of the control device 70 is a linear scale, it divides the spectrum W2 of the optical signal #k by the spectrum W1 of the reference signal. As a result, as shown in FIG. 7(b), the transmittance W3 when all of the FBGs 40-k-1 to 40-k-N formed in the SMF 31-k are transmitted can be obtained. The estimation unit 72 estimates the temperature inside the IoT-GW 100 in the same manner as in the first embodiment based on the relationship between the temperature T obtained in advance and the peak wavelength of the LD21, and the peak wavelength obtained from the spectrum W1. Further, the estimation unit 72 estimates the temperature around each of the FPGs 40-k-1 to 40-k-N in the same manner as in the first embodiment based on the relationship between the temperature T obtained in advance and the Bragg wavelengths of the FBGs 40-k-1 to 40-k-N, and the wavelength of the dip structure in the transmittance W3 obtained by performing data processing on the spectrum W2 of the optical signal #k. ｋ can be obtained. The estimation unit 72 estimates the temperature inside the IoT-GW 100 in the same manner as in the first embodiment based on the relationship between the temperature T obtained in advance and the peak wavelength of the LD21, and the peak wavelength obtained from the spectrum W1. Further, the estimation unit 72 estimates the temperature around each of the FPGs 40-k-1 to 40-k-N in the same manner as in the first embodiment based on the relationship between the temperature T obtained in advance and the Bragg wavelengths of the FBGs 40-k-1 to 40-k-N, and the wavelength of the dip structure in the transmittance W3 obtained by performing data processing on the spectrum W2 of the optical signal #k. ｋ respectively, and the wavelength of the dip structure in the transmittance W3 obtained by performing data processing on the spectrum W2 of the optical signal #k, the temperature around each of the FPGs 40-k-1 to 40-k-N is estimated in the same manner as in the first embodiment. ｋ respectively.

[0052] Note that FBG 40-1-1 to FBG 40-1-N １ , …, 40-(M-1)-1 to FBG 40-(M-1)-N Ｍ－１If the Bragg wavelengths are all different, the spectrum of the optical signal obtained by superimposing optical signals #1 to #(M-1) can be used as spectrum W2.

[0053] Figure 8 shows an MCF35 used in place of all or part of the SMF33-1 to 33-M in Figure 6. The MCF35 has M cores 36-1 to 36-M. Figure 8 shows the case where M=2. For example, a 4-core multicore fiber 35 with M=4 can be used to combine the SMF33-1 to 33-4 into a single fiber. The optical coupler 31 branches the optical signal input from the IoT-GW10 and outputs it to each of the cores 36-1 to 36-M of the MCF35. Each of the cores 36-1 to 36-(M-1) has one or more FBGs 40 formed on it, and no FBG is formed on core 36-M. The data acquisition system branches the optical signals transmitted through each of the cores 36-1 to 36-M using the optical coupler and outputs them to the optical switch 51 as optical signals #1 to #(M-1) and a reference signal.

[0054] As described above, in both configurations using SMF33 and MCF35, by preparing a reference core without processing the FBG40, the spectrum of the reference signal of the LD alone can be obtained. Furthermore, by using this reference signal to process the spectrum of the optical signal after passing through the FBG, the spectrum of the FBG alone can be obtained. Note that the light intensity after passing through the FBG40 is expected to decrease slightly due to scattering loss in the FBG40.

[0055] The operation of the data acquisition system in the second embodiment is the same as that of the data acquisition system in the first embodiment shown in Figure 5. That is, when the IoT-GW100 finishes its period sleep, it receives sensor data from the IoT sensor 82 (step S1). The IoT-GW100 performs predetermined data processing on the received sensor data to generate transmission data and activates the TRx11 of the IoT-GW. The LD12 lights up when the TRx11 is activated. The TRx11 modulates the output light from the LD12 with the transmission data and outputs the generated uplink optical signal to the SMF30-1 (step S2). The optical coupler 31 branches the uplink optical signal into four and outputs them to the SMF33-1 to 33-4.

[0056] Each optical coupler 34-1 to 34-4 branches a portion of the optical signal and outputs it to the optical switch 51. Optical coupler 32 combines the optical signals transmitted through each of the SMFs 34-1 to 34-4 and outputs it to the SMF 30-2. PC 22 receives the optical signal transmitted through the SMF 30-2. PC 22 instructs the control device 70 to start measurement, and the information acquisition unit 71 of the control device 70 sets the optical switch 51 to output the optical signal to the spectrum analyzer 60. Furthermore, the information acquisition unit 71 sets the spectrum analyzer 60 to perform a sweep after the time required for processing in the next steps S4 to S6 has elapsed. The information acquisition unit 71 enters a sweep standby state for the spectrum analyzer. Meanwhile, the control unit 14 of the IoT-GW100 extinguishes the LD 12 of TRx11 and enters a sleep state until it receives an instruction for the next cycle (step S3). When the sleep period ends, the control unit 14 of the IoT-GW100 enters a state of waiting to receive sleep information for the next period (step S4).

[0057] When the next cycle begins, PC22 transmits period sleep information to IoT-GW100. Upon receiving the period sleep information, IoT-GW100 activates TRx11 (step S5). TRx11 causes LD12 to emit light and outputs an optical signal to SMF30-1 (step S6). Optical coupler 31 splits the upstream optical signal into four signals: optical signals #1 to #3 and a reference signal, and outputs them to SMF33-1 to 33-4. Each optical coupler 34-1 to 34-4 splits a portion of the optical signal transmitted through SMF33-1 to 33-4 and outputs it to optical switch 51. Optical switch 51 outputs optical signals #1 to #3 output from optical couplers 34-1 to 34-3 and the reference signal output from optical coupler 34-4 to the spectrum analyzer 60.

[0058] The spectrum analyzer 60 outputs the spectra of optical signals #1 to #3 and the reference signal input from the optical switch 50 to the control device 70. The estimation unit 72 of the control device 70 estimates the temperature inside the housing of the IoT-GW100 based on the wavelength of the peak shown in the spectrum of the reference signal. Furthermore, the estimation unit 72 calculates the N that appears in the transmittance obtained by dividing the spectrum of each optical signal #k by the spectrum of the reference signal.ｋ Based on the wavelength of each dip, FBG40-k-1 to 40-k-N ｋ The temperature around the device is estimated (step S7).

[0059] (Third Embodiment) In the first and second embodiments, a uniform diffraction grating was assumed when obtaining the FBG-induced spectral structure, but the length, pitch, and diffraction grating coupling constant of the diffraction grating may be different values. In the third embodiment, a λ / 4 shift FBG is used.

[0060] Figure 9 shows the transmission characteristics of FBGs and the spectra after transmission through the FBG. Figure 9(a) shows the transmission characteristics F1 of a uniform diffraction grating FBG and the transmission characteristics F2 of a λ / 4 shift FBG. Figure 9(b) shows the dip F3 that appears in the spectrum of the optical signal due to transmission through the transmission characteristics F1 of the uniform diffraction grating FBG, and the peak F4 that appears in the spectrum of the optical signal due to transmission through the transmission characteristics F2 of the λ / 4 shift FBG.

[0061] Although it depends on the length of the diffraction grating and the coupling constant, when using a λ / 4 shift FBG, (1) a steep peak structure is easily obtained, (2) a peak structure appears in the laser spectrum (a dip structure appears with a uniform FBG), and (3) when detecting by transmission peak, the intensity is higher compared to the intensity at the dip. Therefore, it has the advantage of being relatively easy to evaluate. The data acquisition system operates in the same manner as in the first and second embodiments, except that the estimation unit 72 of the control device 70 of this embodiment detects the wavelength of the peak in the LD sideband wavelength range instead of the wavelength of the dip that appears in the optical signal spectrum.

[0062] Hardware configuration examples of the control device 70 used in the first to third embodiments will be described. Figure 10 is a device configuration diagram showing a hardware configuration example of the control device 70. The control device 70 comprises a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0063] The processor 91 is a central processing unit that performs calculations and control. The processor 91 is, for example, a CPU or a GPU (Graphics Processing Unit). The processor 91 reads and executes programs from the memory unit 92. The memory unit 92 further has a work area for when the processor 91 executes various programs. The communication interface 93 connects to other devices for communication. The user interface 94 is an input device such as a keyboard, pointing device (mouse, tablet, etc.), buttons, touch panel, etc., and a display device such as a display. Human operations are input through the user interface 94. For example, various types of information are input through the user interface 94.

[0064] At least some of the functions of the control device 70 are realized by the processor 91 reading and executing a program from the storage unit 92. Note that all or some of these functions may be realized using hardware such as an ASIC, PLD, or FPGA.

[0065] Furthermore, the control device 70 may be implemented by multiple computer devices connected via a network. In this case, the computer devices by which each functional unit of the control device 70 is implemented can be arbitrary. Also, a single functional unit may be implemented by multiple computer devices.

[0066] According to the embodiment described above, temperature can be obtained in a spatial manner based on the spectrum of an optical signal transmitted through one or more transmission wavelength filters with different central wavelengths. Furthermore, by using a signal generated by light output from an LD installed inside the device in addition to the above optical signal, the internal temperature of the device can be obtained simultaneously. In this case, the transmission spectrum of the transmission wavelength filter is superimposed on the spectrum of the light output from the LD.

[0067] Furthermore, the data receiving device can detect the reception of a data signal from the data transmitting device as a trigger, and measure the spectrum in conjunction with the timing of receiving the period sleep information.

[0068] Furthermore, multiple transmission wavelength filters are composed of multiple diffraction gratings with identical or different values ​​for diffraction grating length, pitch, and diffraction grating coupling constant.

[0069] Alternatively, a diffraction grating may be formed in multiple stages on some of the multiple SMFs, while no diffraction grating is formed on the other SMFs. Furthermore, a diffraction grating may be formed in multiple stages on some of the multiple cores of the MCF, while no diffraction grating is formed on the other cores.

[0070] According to the above embodiment, the device temperature and the external temperature can be acquired "simultaneously and in a single operation." Furthermore, the spectrum can be efficiently acquired in accordance with the operation flow of the optical power supply device.

[0071] The temperature estimation device of the above-described embodiment has an estimation unit. The temperature estimation device is, for example, the control device 70 of the embodiment. The estimation unit detects the oscillation peak wavelength of the laser used to generate the optical signal and the center wavelength of the filling of each wavelength filter from the spectrum of an optical signal transmitted through an optical transmission path, which is an optical transmission path formed with one or more wavelength filters that filter wavelength ranges with different center wavelengths, and which filters a portion of the wavelength range of the input light. Based on the detected oscillation peak wavelength, the estimation unit estimates the temperature of the device that generated the optical signal and estimates the temperature around the wavelength filter based on the detected center wavelength.

[0072] Furthermore, multiple wavelength filters may be located at different locations within the temperature measurement area.

[0073] Alternatively, the estimation unit may detect the center wavelength of each wavelength filter based on the result of dividing the spectrum of the optical signal transmitted through the optical transmission path by the spectrum of the optical signal transmitted through the optical transmission path without a wavelength filter, and estimate the temperature around the wavelength filter based on the detected center wavelength.

[0074] A temperature estimation device can also be implemented using a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0075] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments and include designs and the like that do not depart from the spirit of this invention.

[0076] 10 IoT-GW 11 Transceiver (TRx) 13 Photoelectric conversion unit 14 Control unit 15 Communication unit 20 OLT 21 Transceiver (TRx) 22 PC 30, 30-1, 30-2, 33-1 to 33-M Single-mode fiber (SMF) 31, 32, 34-1 to 34-M Optical coupler 35 Multi-core fiber (MCF) 36-1 to 36-M Core 40, 40-1 to 40-N, 40-1-1 to 40-4-3 Fiber Bragg grating (FBG) 50, 51 Optical switch 60 Spectrum analyzer 70 Control unit 71 Information acquisition unit 72 Estimation unit 80 Light source 81 MCF 82 IoT sensor 91 Processor 92 Memory unit 93 Communication interface 94 User interface 100 IoT-GW

Claims

1. A temperature estimation device comprising: a wavelength filter that filters and transmits a portion of the wavelength range of input light, wherein one or more of the wavelength filters are formed on an optical transmission path, each filtering wavelength range with different center wavelengths, and an estimation unit that detects the oscillation peak wavelength of the laser used to generate the optical signal and the center wavelength of the filling of each of the wavelength filters from the spectrum of the optical signal transmitted through the optical transmission path, estimates the temperature of the device that generated the optical signal based on the detected oscillation peak wavelength, and estimates the temperature around the wavelength filter based on the detected center wavelength.

2. The temperature estimation apparatus according to claim 1, wherein the plurality of wavelength filters are located at different locations within the temperature measurement target area.

3. The temperature estimation device according to claim 1 or 2, wherein the estimation unit detects the center wavelength of each of the wavelength filters based on the result of dividing the spectrum of the optical signal transmitted through the optical transmission path by the spectrum of the optical signal transmitted through the optical transmission path without a wavelength filter, and estimates the temperature around the wavelength filter based on the detected center wavelength.

4. A temperature estimation method comprising: an estimation step of detecting the oscillation peak wavelength of a laser used to generate the optical signal and the center wavelength of the filling of each of the wavelength filters from the spectrum of an optical signal transmitted through an optical transmission path in which one or more wavelength filters are formed, each filtering wavelength ranges with different center wavelengths; estimating the temperature of the device that generated the optical signal based on the detected oscillation peak wavelength; and estimating the temperature around the wavelength filters based on the detected center wavelength.

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