Multi-band single-photon OTDR test system and method

Abstract

The embodiment of the invention provides a multi-band single-photon OTDR test system and method, and belongs to the technical field of optical fiber sensing. The system comprises a laser source module used for respectively generating pulsed light of at least two working wavebands according to a preset wavelength sequence; the wave combining and injecting module is used for combining the pulse light of different wave bands into a shared measuring light path and injecting the combined pulse light into the optical fiber to be measured; the echo receiving module is used for receiving multiband backscattered light and reflected light returned by the optical fiber to be detected; the detection link is used for generating a detection signal for representing the arrival time of the photons; the conversion module is used for forming multiband time domain scattering data; and the processing module is used for generating a corresponding multiband OTDR measurement result based on the multiband time domain scattering data. According to the scheme of the invention, multiband single-photon OTDR measurement is realized in a unified optical path and a unified detection link, so that scattering information of different bands is synchronously acquired under the same time reference and distance scale.

Description

A multi-band single-photon OTDR testing system and method Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, specifically to a multi-band single-photon OTDR testing system and a multi-band single-photon OTDR testing method. Background Technology

[0002] Optical Time Domain Reflectometry (OTDR) technology, as a common method for analyzing the condition of optical fiber links, is widely used in scenarios such as communication cable testing, structural health monitoring, and low-light sensing. Traditional OTDR devices typically operate in a single wavelength band, determining the loss distribution and reflection characteristics of the fiber by measuring the time distribution of backscattered and reflected light. However, due to the differences in scattering characteristics, attenuation characteristics, and sensitivity to structural defects in different wavelength bands of optical fibers, single-band measurements are often insufficient to comprehensively characterize the condition of the optical fiber link, especially when it is necessary to simultaneously identify multiple types of characteristics such as bending loss, connector reflection, and local structural changes.

[0003] To improve measurement coverage, multi-band OTDRs are gaining increasing attention. Existing multi-band OTDRs typically use multiple lasers and multiple detection channels to perform measurements in different bands. The testing process requires repeated executions, resulting in large system size, complex structure, and a lack of unified reference and consistent time scale between different band measurements. This makes the alignment and fusion of multi-band data difficult, hindering the acquisition of continuous multi-band scattering information on the same distance axis.

[0004] On the other hand, for measurement needs in long-distance, weak-signal scenarios, single-photon detection technology has been applied to a new generation of high-sensitivity OTDR systems. Single-photon OTDRs can convert echo signals into time histograms through single-photon counting, significantly improving the measurability of weak scattering signals. However, most existing single-photon OTDRs are still limited to single-band measurements, and their detection links are usually optimized for specific wavelengths, making it difficult to be compatible with multi-band signals in the same detection path.

[0005] In summary, in the existing technology, multi-band measurement and single-photon detection have not yet formed a unified system architecture, making it difficult to achieve co-path propagation of multi-band pulsed light, unified reception of return light, and sensitive detection in shared detection links. As a result, the integration, stability, and data consistency of multi-band time-domain measurement systems are all somewhat lacking. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-band single-photon OTDR testing system and method to at least solve the problem that multi-band measurements require multiple independent tests and cannot be completed in a unified detection link.

[0007] To achieve the above objectives, the first aspect of the present invention provides a multi-band single-photon OTDR testing system, the system comprising: a laser source module for generating pulsed light of at least two working bands according to a preset wavelength sequence; a combining and injection module connected to the laser source module for combining pulsed light of different bands into a shared measurement optical path and injecting the combined pulsed light into the optical fiber under test; an echo receiving module disposed on the echo path of the optical fiber under test for receiving multi-band backscattered light and reflected light returned by the optical fiber under test and outputting it to a detection link; a detection link connected to the echo receiving module for performing single-photon detection on the echo light from each band in a unified detection path and generating a detection signal for characterizing the photon arrival time; a conversion module connected to the detection link for time-stamping the detection signal to form multi-band time-domain scattering data; and a processing module connected to the conversion module for generating corresponding multi-band OTDR measurement results based on the multi-band time-domain scattering data.

[0008] Optionally, the laser source module includes multiple pulsed lasers corresponding to different wavelength bands, and a wavelength scheduling control unit connected to each pulsed laser; the wavelength scheduling control unit is used to drive each pulsed laser to output pulsed light sequentially according to a preset wavelength sequence, so that the combining and injection module obtains the time segmented sequence of multi-band pulsed light as the input for subsequent combining.

[0009] Optionally, the multiplexing and injection module includes a wavelength division multiplexer and an injection optical path; the wavelength division multiplexer is used to combine pulsed light from different wavelength bands into a single optical path according to the optical channel rules corresponding to each wavelength band; the injection optical path guides the combined pulsed light to the input end of the optical fiber under test.

[0010] Optionally, the echo receiving module includes a broadband circulator and a pre-optical processing unit; the broadband circulator is used to separate the pulse light injected into the fiber under test from the multi-band light returning from the fiber under test; the pre-optical processing unit is used to perform optical power shaping on the returned light and output the shaped returned light to the probe link.

[0011] Optionally, the detection link includes a wavelength division unit and at least one single-photon detector; the wavelength division unit is used to distribute the optical signal to the corresponding single-photon detector according to the wavelength characteristics of the returned light; the single-photon detector is used to convert the photon event into a detection signal of the detection link and output it to the conversion module.

[0012] Optionally, the detection link further includes an optical gating unit; the optical gating unit is disposed between the wavelength division unit and the single-photon detector, and is used to selectively transmit return light according to a set time window, so that the conversion module obtains photon event data within the corresponding detection time window.

[0013] Optionally, the conversion module includes a time-to-digital converter and an event identification unit; the event identification unit is used to identify the event identification code of the corresponding band for the probe signal; the time-to-digital converter is used to generate time-domain scattering data with band labels based on the event identification code and the probe signal and output it to the processing module.

[0014] Optionally, the processing module includes a multi-band data alignment unit and a feature extraction unit; the multi-band data alignment unit is used to perform time-base calibration on time-domain scattering data of different bands and construct a unified distance axis; the feature extraction unit is used to calculate multi-band scattering features on the unified distance axis to generate multi-band OTDR measurement results.

[0015] A second aspect of the present invention provides a multi-band single-photon OTDR testing method, which is implemented based on the aforementioned multi-band single-photon OTDR testing system. The method includes: generating pulsed light of at least two bands according to a preset wavelength sequence using a laser source module, and outputting the generated pulsed light to a combining and injection module; combining the pulsed light of different bands into a shared measurement optical path using the combining and injection module, and injecting the combined pulsed light into the optical fiber under test; receiving multi-band backscattered light and reflected light returned from the optical fiber under test using an echo receiving module, and outputting the returned light to a detection link; performing single-photon detection on the returned light from each band using the detection link to obtain a detection signal characterizing the photon arrival time, and outputting the detection signal to a conversion module; performing time stamping on the detection signal using the conversion module to form multi-band time-domain scattering data, and generating corresponding multi-band OTDR measurement results using a processing module based on the multi-band time-domain scattering data.

[0016] On the other hand, the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described multi-band single-photon OTDR testing method.

[0017] By employing the aforementioned technical solution, and by setting up a laser source module to generate multi-band pulsed light according to a preset wavelength sequence, this invention can obtain incident signals from multiple working bands within the same measurement cycle. The combining and injection module combines the pulsed light from each band into a shared optical path, allowing multi-band signals to propagate in the same fiber optic path, avoiding the path differences and repetitive debugging problems caused by traditional multiple independent tests. The echo receiving module uniformly acquires multi-band backscattered and reflected light and sends them to the detection link, enabling single-photon-level detection of return signals from different bands in the same detection path. The conversion module performs unified time stamping on all detection signals, thereby constructing multi-band scattering data with a common time reference. The processing module generates multi-band OTDR measurement results on a unified time axis, achieving synchronous acquisition and consistent expression of cross-band data. Therefore, this invention effectively solves the problems of multi-band measurements being unable to share detection links and lacking a unified scale for results, improving the consistency and integration of multi-band testing.

[0018] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the drawings: Figure 1 is a system structure diagram of a multi-band single-photon OTDR testing system provided in one embodiment of the present invention; Figure 2 is a schematic diagram of the optical path and detector link structure of a multi-band single-photon OTDR testing system provided in one embodiment of the present invention; Figure 3 is a flowchart of the steps of a multi-band single-photon OTDR testing method provided in one embodiment of the present invention; Figure 4 is an internal structure diagram of a computer device provided in one embodiment of the present invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] As shown in Figure 1, this embodiment of the invention provides a multi-band single-photon OTDR testing system. The system includes: a laser source module for generating pulsed light of at least two working bands according to a preset wavelength sequence; a combining and injection module connected to the laser source module for combining pulsed light of different bands into a shared measurement optical path and injecting the combined pulsed light into the optical fiber under test; an echo receiving module disposed on the echo path of the optical fiber under test for receiving multi-band backscattered light and reflected light returned by the optical fiber under test and outputting it to a detection link; a detection link connected to the echo receiving module for performing single-photon detection on the echo light from each band in a unified detection path and generating a detection signal to characterize the photon arrival time; a conversion module connected to the detection link for time-stamping the detection signal to form multi-band time-domain scattering data; and a processing module connected to the conversion module for generating corresponding multi-band OTDR measurement results based on the multi-band time-domain scattering data.

[0022] In this embodiment of the invention, a multi-band single-photon OTDR testing system is constructed, consisting of a laser source module, a multiplexing and injection module, an echo receiving module, a detection link, a conversion module, and a processing module. This system forms an overall architecture capable of performing multi-band measurements under a unified optical path and a unified detection path. The laser source module outputs pulsed light of at least two working bands according to a preset wavelength sequence, providing basic light source scheduling capabilities for multi-band time-domain measurements. The multiplexing and injection module combines pulsed light of different bands into a shared measurement optical path and injects it into the fiber under test, ensuring that signals of each band propagate in the same transmission path, thus eliminating path differences caused by multiple independent measurements in traditional multi-band testing.

[0023] During the return light acquisition process, the echo receiving module uniformly receives multi-band backscattered and reflected light from the fiber under test and transmits it to the probe link, enabling the entire system to collect multi-band signals within a single echo path. The probe link performs single-photon detection on the return light of different bands within a unified detection path, ensuring that weak scattering signals can be detected with high sensitivity across multiple bands and converted into detection signals characterizing photon arrival times. The conversion module applies a unified time stamp to these detection signals, constructing multi-band time-domain scattering data with a common time reference, laying the foundation for cross-band data alignment and joint analysis. Finally, the processing module generates corresponding multi-band OTDR measurement results based on this time-domain scattering data, allowing the loss characteristics of different bands to be presented on the same scale.

[0024] Through the above structural combination, the present invention establishes a highly integrated, path-consistent technical framework that enables multi-band measurements at single-photon sensitivity, providing a foundation for further development of optical path configuration, detection structure, data generation and processing strategies in subsequent embodiments.

[0025] Preferably, the laser source module includes multiple pulsed lasers corresponding to different wavelength bands, and a wavelength scheduling control unit connected to each pulsed laser; the wavelength scheduling control unit is used to drive each pulsed laser to output pulsed light sequentially according to a preset wavelength sequence, so that the combining and injection module obtains the time segmented sequence of multi-band pulsed light as the input for subsequent combining.

[0026] In this embodiment of the invention, the laser source module is configured for multi-band OTDR applications and includes multiple pulsed lasers, each operating in a preset wavelength band, such as commonly used detection wavelengths like 850nm, 1310nm, and 1550nm. Each pulsed laser is structurally independently arranged, possessing a separate drive interface and trigger input, facilitating the setting of different pulse widths, repetition frequencies, and average power according to wavelength characteristics. The outputs of the multiple pulsed lasers correspond one-to-one with the control channels of the wavelength scheduling control unit. The wavelength scheduling control unit electrically manages each pulsed laser through its own channel, thus forming a programmable multi-band pulsed light source platform. This modular configuration provides a clear wavelength division and independent timing control basis for subsequent multiplexing and injection processes.

[0027] The wavelength scheduling control unit drives each pulsed laser to output pulsed light sequentially according to a preset wavelength sequence. This preset wavelength sequence can be stored in a table format on a storage medium, with each entry including at least the band identifier, pulse trigger time, number of pulses, and repetition order within a single measurement cycle. During a complete measurement cycle, the wavelength scheduling control unit sends trigger signals to the corresponding pulsed lasers according to this sequence table and in chronological order, causing different bands to generate pulse outputs within non-overlapping time windows. The multi-band pulsed light received by the multiplexing and injection module thus appears as a time-segmented sequence, with each time segment containing only a single band of pulsed light. The band switching relationship within the entire measurement cycle is explicitly defined by the preset wavelength sequence. Through this scheduling rule, the multi-band pulsed light is segmented and identified in the time domain before entering the multiplexing and injection module, facilitating subsequent timing correspondence and band differentiation within a unified optical path and unified detection link. This is beneficial for obtaining multi-band OTDR measurement data with a unified time reference.

[0028] Preferably, the wavelength division multiplexing and injection module includes a wavelength division multiplexer and an injection optical path; the wavelength division multiplexer is used to combine pulsed light from different wavelength bands into a single optical path according to the optical channel rules corresponding to each wavelength band; the injection optical path guides the combined pulsed light to the input end of the optical fiber under test.

[0029] In this embodiment of the invention, the multiplexing and injection module mainly completes the unified organization of multi-band pulsed light along the spatial path. The module includes a wavelength division multiplexer (WDM multiplexer), which pre-divides several optical channels, each corresponding to a working wavelength band. For example, in common implementations, these correspond to three wavelength bands: 850nm, 1310nm, and 1550nm. The output of each pulsed laser is connected to the corresponding channel port of the WDM multiplexer via fiber optic patch cords or fiber optic pigtails. The center wavelength and bandwidth of the channel port are selected according to the target wavelength band to ensure transmission within that band while providing suppression for other bands. Through this channel correspondence, multiple wavelength bands are combined into a single output optical path within the WDM multiplexer according to preset rules, forming a multi-band pulse sequence at the output that includes time-segmented and wavelength-segmented information.

[0030] The injection optical path is responsible for stably guiding the combined pulsed light to the input end of the fiber under test (DUT). Structurally, it typically includes a fiber optic connector, fiber optic patch cords, and an adapter unit for connecting to the DUT. To reduce interference from reflections on the preceding laser source and the subsequent probe link, an optical isolator can be connected in series in the injection optical path to suppress reflected light returning from the DUT and propagating back to the front end. When it is necessary to control the incident power, an adjustable optical attenuator can also be configured in the injection optical path to set an appropriate input power level for different measurement scenarios. The end of the injection optical path is connected to the input end of the DUT via a standard interface or fusion splice. The end-face quality and matching method at the connection point determine the coupling efficiency and initial reflection characteristics.

[0031] In multi-band single-photon OTDR applications, the aforementioned configuration of the multiplexing and injection modules allows pulsed light of different bands to share the same physical transmission path, with the temporal sequence and spatial path uniformly established on the combined structure of the wavelength division multiplexer and the injection optical path. This ensures good consistency in the path between the backscattered and reflected light generated in the fiber under test, allowing subsequent echo reception and single-photon detection stages to process multi-band scattering data under a unified reference. Overall, this module design provides stable fiber insertion conditions and a repeatable optical path environment for multi-band measurements, facilitating the analysis of loss and reflection characteristics at different bands on the same distance scale.

[0032] Preferably, the echo receiving module includes a broadband circulator and a pre-optical processing unit; the broadband circulator is used to separate the pulse light injected into the fiber under test from the multi-band light returning from the fiber under test; the pre-optical processing unit is used to perform optical power shaping on the returned light and output the shaped returned light to the probe link.

[0033] In this embodiment of the invention, the echo receiving module primarily handles the path separation of the forward-injected light and the backward-returning light. The echo receiving module includes a broadband circulator and a pre-optical processing unit. The broadband circulator operates within a multi-band range, covering all operating bands selected by the laser source module. The broadband circulator is configured with a multi-port structure: the first port connects to the output of the combining and injection module, the second port connects to the input of the fiber under test, and the third port connects to the input of the pre-optical processing unit. The pulsed light injected via the first port is transmitted along a predetermined direction to the second port and enters the fiber under test, while the multi-band light returning from the fiber under test is coupled from the second port to the third port and transmitted to the pre-optical processing unit, thereby achieving optical path separation of the forward pulsed light and the backward-returning light in the physical path.

[0034] Broadband circulators need to maintain low insertion loss and high port isolation within the target wavelength range. When the insertion loss is controlled within a preset range, backscattered and reflected light in the fiber under test can reach the front-end optical processing unit at a high power level. When the port isolation meets the design requirements, stray light from the probe link direction is less likely to backflow into the multiplexing and injection modules, and forward injected light is less likely to enter the probe link through undesired paths. This isolation effect is beneficial for stabilizing the single-photon detection process. After the broadband circulator's operating bandwidth covers a multi-wavelength range, multi-wavelength return light can be uniformly received in the echo reception stage without the need for segmented switching devices, resulting in a relatively simple overall optical path structure.

[0035] The pre-optical processing unit performs optical power shaping on the return light output from the broadband circulator. This unit may include components such as an adjustable optical attenuator, a limiting device, and a bandpass filter to control the average power and spectral composition of the return light. The adjustable attenuator sets the attenuation amount according to the dynamic range of the probe link, ensuring the photon count rate received by the single-photon detector falls within the expected range, preventing excessive power from causing saturation or dead-time accumulation. The bandpass filter is designed with a passband appropriate for multi-band operation, suppressing unwanted amplified spontaneous emission and ambient stray light, and reducing background noise. If necessary, a polarization controller can also be introduced into the pre-optical processing unit to pre-adjust the polarization state of the return light, thereby improving the stability of the fiber optic connection in the probe link.

[0036] After being shaped by the pre-optical processing unit, the returned light is output to the detection link. The optical power level, spectral range, and polarization state are limited to the working range suitable for single-photon detection. With this configuration, the echo receiving module forms a unified returned light entry condition in multi-band measurements, so that the backscattered and reflected light of different bands have relatively consistent optical characteristics before entering the detection link. This facilitates obtaining stable and comparable multi-band time-domain scattering data in the subsequent single-photon counting and time-stamping stages.

[0037] Preferably, the detection link includes a wavelength division unit and at least one single-photon detector; the wavelength division unit is used to distribute the optical signal to the corresponding single-photon detector according to the wavelength characteristics of the returned light; the single-photon detector is used to convert the photon event into a detection signal of the detection link and output it to the conversion module.

[0038] In this embodiment of the invention, a wavelength division unit (WDM) and at least one single-photon detector are provided in the detection link. The input end of the WDM is connected to the output end of the pre-optical processing unit, and the output end is connected to the optical input end of the single-photon detector. The WDM typically employs a wavelength division multiplexing (WDM) or multi-port filter structure to allocate independent optical paths for return light of different wavelength bands, with each optical path corresponding to a preset wavelength range. Through this physical division method, the multi-band return light has already undergone wavelength band differentiation before entering the single-photon detector, reducing the burden of wavelength discrimination in subsequent electrical signal processing.

[0039] The channel configuration of the wavelength division unit (WDM) needs to match the operating wavelength of the laser source module. Each WDM channel has a set center wavelength and bandwidth parameters. The center wavelength falls near the target operating wavelength, and the bandwidth is determined based on the spectral width of the scattered signal and the device performance. When thin-film filters, arrayed waveguide gratings, or other integrated WDM structures are used inside the WDM, multi-channel separation can be achieved in a smaller volume, and crosstalk between channels can be controlled within a preset range. After the return light completes spectral selection within the WDM, optical signals of different wavelengths enter the subsequent single-photon detector through their respective output ports. The correspondence is fixed in the design stage and does not rely on subsequent software identification.

[0040] Single-photon detectors are used to convert photon events into electrical signals. Short-wavelength return light can be configured with a silicon-based SPAD (Single-Photon Avalanche Diode) detector, while long-wavelength return light can be configured with an InGaAs SPAD detector. Each single-photon detector operates within the high quantum efficiency range of its corresponding wavelength band. With the aid of a bias circuit, the single-photon detector operates in Geiger mode, generating a pulse output with identifiable amplitude for each incident photon. Preamplifier and shaping circuits can be added to the detection link as needed to convert the raw current pulse output by the single-photon detector into a standard voltage pulse that meets the input requirements of the conversion module. Each photon event corresponds to a rising edge or trigger edge on the time axis; these trigger edges are transmitted to the time measurement channel of the conversion module via cables or printed circuit board traces.

[0041] By combining a wavelength division unit and a single-photon detector, the detection link completes the band differentiation of multi-band return light and single-photon-level photoelectric conversion. After receiving the detection signals from each band, the conversion module can record the photon arrival time under a unified time reference, providing a foundation for constructing multi-band time-domain scattering data. Overall, this detection link structure maintains the wavelength resolution required for multi-band measurements while also taking into account the requirements of low noise and standardized electrical signals for single-photon detection, which is beneficial for obtaining stable and comparable multi-band OTDR measurement results in subsequent data processing.

[0042] Preferably, the detection link further includes an optical gating unit; the optical gating unit is disposed between the wavelength division unit and the single-photon detector, and is used to selectively transmit return light according to a set time window, so that the conversion module obtains photon event data within the corresponding detection time window.

[0043] In this embodiment of the invention, the optical gating unit is primarily responsible for time selection in a multi-band single-photon OTDR. The optical gating unit is positioned between each output of the wavelength division unit and the input of the corresponding single-photon detector. Each return beam passes through an independent gating channel before entering the single-photon detector. The gating channel can employ an acousto-optic modulator, an electro-optic modulator, or other fast optical switch structures, with the switching state driven by an external gating control signal. In this way, the return beam is only allowed to pass through the optical gating unit within a set time window; light signals falling outside the time window are suppressed at the front end of the gating channel.

[0044] The time window setting is typically related to the laser pulse emission time and the length range of the fiber under test. The gating control signal calculates the opening and closing times according to the measurement distance interval. The opening time corresponds to the round-trip propagation time of the target interval, and the closing time corresponds to the round-trip propagation time at the end of the interval. For the same wavelength band, the time window can be shifted sequentially within multiple measurement cycles to cover different distance segments with multiple acquisitions. For different wavelength bands, the gating timing can be fine-tuned based on differences in refractive index and group velocity. Through this time selection strategy, the optical gating unit completes segment division in the spatial dimension and limits the acquisition window in the temporal dimension.

[0045] The single-photon detector after the optical gating unit only receives return light within the time window, so the detection signal received by the conversion module naturally carries a clear distance range meaning. When recording photon events, the conversion module does not need to determine whether they belong to the valid measurement range again; it only needs to time-mark the rising edge of the pulse during the effective gating period. Dark counts and environmental scattering outside the gating are partially truncated, background event density decreases, and noise levels unrelated to the target range in the time histogram are controlled. Overall, this gating configuration provides an adjustable acquisition window for multi-band single-photon measurements, making the photon event data obtained by the conversion module more concentrated within the preset detection time window, which helps to subsequently construct a segmented and clearly defined time-domain scattering distribution.

[0046] Preferably, the conversion module includes a time-to-digital converter and an event identification unit; the event identification unit is used to identify the event identification code of the corresponding band for the probe signal; the time-to-digital converter is used to generate time-domain scattering data with band labels based on the event identification code and the probe signal and output it to the processing module.

[0047] In this embodiment of the invention, the conversion module includes a time-to-digital converter and an event identification unit, which operate in series on the signal link. The event identification unit receives probe signals from the probe link and simultaneously receives band-related control information. It generates an event identification code by mapping these two types of information. The event identification code contains at least a band number, and may also include a channel number or measurement period number as needed. The bit positions of different fields are fixed using encoding rules to facilitate subsequent parsing. After processing by the event identification unit, each probe signal is bound to a unique event identification code, forming a digital event stream with band attributes, which is then sent to the input of the time-to-digital converter.

[0048] The time-to-digital converter (TDD) measures the time of a probe signal with an event identifier code. Using the laser trigger signal or a reference clock as the zero point, the TDD quantizes the arrival time of the probe signal. Common configurations internally construct subdivided time intervals to achieve picosecond to nanosecond time resolution. The TDD records the event identifier code while simultaneously recording the timestamp, combining the two data parts for output, forming time-domain scattering data with band labels.

[0049] Time-domain scattering data can be organized into an event sequence according to a fixed format. Each event includes a timestamp field and a band label field. The timestamp field corresponds to the round-trip propagation time of the photon, and the band label field indicates which operating band the photon originated from. After reading this event sequence, the processing module constructs a multi-band time histogram based on the timestamp and band label, and counts the photons in different bands on a unified time axis. Through this conversion rule, multi-band measurements obtain a unified time reference and clear band distinction at the hardware level, providing a data foundation for subsequent analysis of multi-band scattering characteristics under the same distance scale.

[0050] Preferably, the processing module includes a multi-band data alignment unit and a feature extraction unit; the multi-band data alignment unit is used to perform time-base calibration on time-domain scattering data of different bands and construct a unified distance axis; the feature extraction unit is used to calculate multi-band scattering features on the unified distance axis to generate multi-band OTDR measurement results.

[0051] In this embodiment of the invention, the processing module includes a multi-band data alignment unit and a feature extraction unit. The multi-band data alignment unit first receives time-domain scattering data of each band from the conversion module, with each band's data based on photon event time. The multi-band data alignment unit converts the time axis into a distance axis based on the laser triggering time, repetition period, and preset refractive index parameters, and corrects for zero-point offsets and time delay offsets generated by different bands. If necessary, the multi-band data alignment unit can also consider the influence of dispersion on the propagation speed of different bands, introducing band-related refractive index or group velocity parameters into the distance conversion to ensure that the distance coordinates corresponding to the same physical location are consistent across bands. After multiple rounds of processing, the multi-band data alignment unit outputs a set of shared distance coordinates, constructing a multi-band scattering data set on a unified distance axis.

[0052] The feature extraction unit performs quantitative analysis of multi-band scattering data on a unified distance axis. The feature extraction unit can calculate parameters such as backscattering intensity, local slope, differential loss, and reflection peak amplitude for each band of scattering data according to a preset distance sampling interval, and combine the results of different bands at the same distance location into a multi-dimensional feature vector. For locations with obvious reflections or abrupt changes, the feature extraction unit can perform peak search and step detection within the neighborhood to distinguish between joint reflections, connector reflections, and slowly varying loss characteristics caused by bending. When a standard OTDR curve needs to be output, the feature extraction unit reconstructs the loss curves of each band based on the multi-band scattering intensity and distance coordinates, or generates a multi-band comparison graph on a unified distance axis. Finally, the multi-band data alignment unit and the feature extraction unit work together to provide multi-band OTDR measurement results with a unified distance scale and multi-band scattering characteristics, which is beneficial for identifying the loss distribution and reflection locations in fiber optic links under the same spatial reference.

[0053] In one specific implementation, the multi-band single-photon OTDR test setup is arranged around a unified modulation and detection link. Multiple pulsed lasers corresponding to different wavelengths are sequentially connected to their respective input ports. Each laser output is connected to a shared optical attenuator via an independent fiber optic patch cord. This attenuator maintains stable transmittance across the entire wavelength range, used to adjust the input power and limit the impact of strong pulses on subsequent devices. The attenuated multi-band pulsed light sequentially enters the same optical circulator, injected into the fiber under test through the main channel, and receives backscattered and reflected light from the fiber under test through another channel. The optical circulator needs to be configured with versions covering each target wavelength to match the band-dependent coupling performance.

[0054] The returned light, after passing through an optical circulator, enters an acousto-optic modulator. This modulator employs a broadband design, enabling gated modulation of the returned light across different wavelengths. The gate trigger is provided by a delay generator, which generates a gated time window based on a predetermined pulse sequence. The gated returned light is then fed into a single-photon detector. Different wavelengths correspond to detectors with different material platforms; for example, silicon-based single-photon avalanche diodes are used for short wavelengths, while InGaAs devices are used for long wavelengths. The electrical signal output from the detector is input to a digital time converter, which performs unified time marking. The host computer interacts with the delay generator and the digital time converter to perform multi-band pulse scheduling, data collection, and time-domain scattering curve generation.

[0055] As shown in Figure 2, in one specific embodiment, the optical path of the single-photon OTDR is configured according to the illustrated structure. The laser source module outputs pulsed light with a preset wavelength sequence. The pulsed light first enters the optical attenuator, which is used to set the input power and provide consistent input conditions for different wavelength bands. The attenuated pulsed light enters the incident port of the optical circulator and is transmitted along the forward channel of the optical circulator to the fiber under test. Backscattered light and multiple types of reflected light are formed in the fiber under test. These returning lights return to the echo port of the optical circulator along the same path. The echo port of the optical circulator directs the returning light to the acousto-optic modulator. The acousto-optic modulator selectively allows the returning light according to the external gate control signal to obtain the scattering event sequence within the corresponding distance range. After gating processing by the acousto-optic modulator, the remaining returning light enters the single-photon detector. The detector operates in Geiger mode, generating electrical pulses for individual photon events and outputting them to the time conversion module.

[0056] In this implementation, the laser source module to the fiber under test constitutes a complete forward optical path, and the fiber under test to the single-photon detector constitutes a unified echo detection path. The entire optical path structure ensures that the forward injection and echo detection paths are consistent, which helps to obtain aligned time-domain scattering data at different wavelengths.

[0057] As shown in Figure 3, this embodiment of the invention provides a multi-band single-photon OTDR testing method. The system includes: the method is implemented based on the multi-band single-photon OTDR testing system according to any one of claims 1-8. The method includes: step S10: the laser source module generates pulse light of at least two bands according to a preset wavelength sequence, and outputs the generated pulse light to the combining and injection module.

[0058] Specifically, the laser source module sequentially generates pulsed light in at least two working wavelength bands according to a pre-set wavelength sequence. The pre-set wavelength sequence defines the output order of the pulsed light in different wavelength bands on the time axis, ensuring that each wavelength band pulsed light is generated sequentially in time segments within the same measurement period. When outputting pulsed light, the laser source module can set pulse width, pulse repetition frequency, or transmission power parameters for different working wavelength bands to adapt to the attenuation and scattering characteristics of different wavelength bands in the optical fiber. After generation, each wavelength band pulsed light is not directly injected into the fiber under test, but is instead uniformly output to the multiplexing and injection module as the input optical signal for subsequent multiplexing processing. Through this step, the timing organization of multi-wavelength pulsed light can be completed at the transmitting end, providing the basic light source scheduling conditions for subsequent multi-wavelength OTDR testing in a shared measurement optical path.

[0059] Step S20: Based on the multiplexing and injection module, pulses of different wavelengths are combined into a shared measurement optical path, and the combined pulses are injected into the optical fiber under test.

[0060] Specifically, the combining and injection module receives pulsed light of different wavelengths from the laser source module and combines them into a shared measurement optical path according to a preset optical channel rule. During the combining process, the pulsed light of each wavelength is spatially guided to the same output optical path, but in time it still maintains the segmented characteristics defined by the preset wavelength sequence. After combining, the multi-band pulsed light is injected into the input end of the fiber under test via the injection optical path, allowing the pulsed light of different wavelengths to propagate in the same physical fiber. Since the pulsed light of each wavelength shares the measurement optical path and the path of the fiber under test, this step can avoid the path differences caused by multiple independent measurements, providing consistent propagation conditions for the subsequent analysis of echo signals under a unified time reference and a unified distance scale.

[0061] Step S30: Receive the multi-band backscattered light and reflected light returned by the optical fiber under test based on the echo receiving module, and output the returned light to the probe link.

[0062] Specifically, the echo receiving module is positioned on the echo path of the optical fiber under test (IDT) to receive the backscattered and reflected light generated by multi-band pulsed light excitation in the IDT. The backscattered and reflected light return along the original propagation path and are separated from the injection optical path by the echo receiving module. When receiving the returned light, the echo receiving module receives echoes of different bands uniformly without distinction, ensuring that multi-band echo signals are transmitted along the same echo path. The multi-band echo light processed by the echo receiving module is output to the detection link as the input signal for subsequent single-photon detection. This step maintains the path consistency of the multi-band signals on the echo side, laying the foundation for single-photon detection in the unified detection link.

[0063] Step S40: Perform single-photon detection on the return light from each band based on the detection link to obtain the detection signal characterizing the arrival time of the photon, and output the detection signal to the conversion module.

[0064] Specifically, the detection link performs single-photon detection processing on the multi-band echo light from the echo receiving module. The detection link performs photoelectric conversion on the echo light of different bands within a unified detection path, converting the incident photon events into corresponding detection signals. Each detection signal characterizes the time information of a single photon arriving at the detection link, thus mapping the optical echo information to the time domain. The detection signal output by the detection link is sent to the conversion module in the form of an electrical signal as input for time stamping processing. By performing single-photon detection on the echo light of each band within the same detection link, consistent time reference and detection conditions can be ensured for the detection processes of different bands, which is beneficial for the unified processing of subsequent multi-band time-domain data.

[0065] Step S50: The detection signal is time-stamped by the conversion module to form multi-band time-domain scattering data, and the processing module generates the corresponding multi-band OTDR measurement results based on the multi-band time-domain scattering data.

[0066] Specifically, the conversion module performs time-stamping processing on the probe signals from the probe link to generate multi-band time-domain scattering data. The time-stamping process uses a preset reference time as a benchmark, recording the arrival time of the photons corresponding to each probe signal, thus forming time-domain data reflecting the round-trip propagation time of the photons. This multi-band time-domain scattering data is then input to the processing module, which generates corresponding multi-band OTDR measurement results based on the time-domain scattering data. The processing module can organize and express data from different bands on a unified time axis or distance axis, enabling the multi-band OTDR measurement results to reflect the scattering and reflection characteristics distribution of the optical fiber under test in different operating bands.

[0067] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described multi-band single-photon OTDR testing method.

[0068] In one embodiment, a computer device, which may be a server, is provided, and its internal structure is shown in Figure 4. The computer device includes a processor A01, a network interface A02, a memory (not shown in the figure), and a database (not shown in the figure) connected via a system bus. The processor A01 provides computing and control capabilities. The memory includes internal memory A03 and a non-volatile storage medium A04. The non-volatile storage medium A04 stores an operating system B01, a computer program B02, and a database (not shown in the figure). The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 stored in the non-volatile storage medium A04. The network interface A02 is used to communicate with external terminals via a network connection. When the computer program B02 is executed by the processor A01, it implements a multi-band single-photon OTDR testing method.

[0069] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0070] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0071] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A multi-band single-photon OTDR testing system, characterized in that, The system includes: a laser source module for generating pulsed light in at least two working wavelength bands according to a preset wavelength sequence; a combining and injection module connected to the laser source module for combining pulsed light from different wavelength bands into a shared measurement optical path and injecting the combined pulsed light into the fiber under test; an echo receiving module located on the echo path of the fiber under test for receiving multi-band backscattered light and reflected light returned by the fiber under test and outputting it to the detection link; a detection link connected to the echo receiving module for performing single-photon detection on the echo light from each wavelength band in a unified detection path and generating a detection signal to characterize the photon arrival time; a conversion module connected to the detection link for time-stamping the detection signal to form multi-band time-domain scattering data; and a processing module connected to the conversion module for generating corresponding multi-band OTDR measurement results based on the multi-band time-domain scattering data.

2. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The laser source module includes multiple pulsed lasers corresponding to different wavelength bands, and a wavelength scheduling control unit connected to each pulsed laser. The wavelength scheduling control unit is used to drive each pulsed laser to output pulsed light sequentially according to a preset wavelength sequence, so that the combining and injection module obtains the time segmented sequence of multi-band pulsed light as the input for subsequent combining.

3. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The wavelength division multiplexing and injection module includes a wavelength division multiplexer and an injection optical path; the wavelength division multiplexer is used to combine pulsed light of different wavelength bands into a single optical path according to the optical channel rules corresponding to each wavelength band; the injection optical path guides the combined pulsed light to the input end of the optical fiber under test.

4. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The echo receiving module includes a broadband circulator and a front-end optical processing unit; the broadband circulator is used to separate the pulse light injected into the optical fiber under test from the multi-band light returning from the optical fiber under test. The front-end optical processing unit is used to perform optical power shaping on the returned light and output the shaped returned light to the detection link.

5. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The detection link includes a wavelength division unit and at least one single-photon detector; the wavelength division unit is used to distribute the optical signal to the corresponding single-photon detector according to the wavelength characteristics of the returned light; the single-photon detector is used to convert the photon event into a detection signal of the detection link and output it to the conversion module.

6. The multi-band single-photon OTDR testing system according to claim 5, characterized in that, The detection link also includes an optical gating unit; the optical gating unit is located between the wavelength division unit and the single-photon detector, and is used to selectively transmit return light according to a set time window so that the conversion module can obtain photon event data within the corresponding detection time window.

7. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The conversion module includes a time-to-digital converter and an event identification unit; the event identification unit is used to identify the event identification code of the corresponding band for the probe signal; the time-to-digital converter is used to generate time-domain scattering data with band labels based on the event identification code and the probe signal and output it to the processing module.

8. The multi-band single-photon OTDR testing system according to claim 1, characterized in that, The processing module includes a multi-band data alignment unit and a feature extraction unit; the multi-band data alignment unit is used to perform time-base calibration on time-domain scattering data of different bands and construct a unified distance axis; the feature extraction unit is used to calculate multi-band scattering features on the unified distance axis to generate multi-band OTDR measurement results.

9. A multi-band single-photon OTDR testing method, characterized in that, The method is implemented based on the multi-band single-photon OTDR testing system according to any one of claims 1-8. The method includes: generating pulsed light of at least two bands according to a preset wavelength sequence by a laser source module, and outputting the generated pulsed light to a combining and injection module; combining the pulsed light of different bands into a shared measurement optical path based on the combining and injection module, and injecting the combined pulsed light into the optical fiber under test; receiving multi-band backscattered light and reflected light returned by the optical fiber under test by an echo receiving module, and outputting the returned light to a detection link; performing single-photon detection on the returned light from each band based on the detection link to obtain a detection signal characterizing the photon arrival time, and outputting the detection signal to a conversion module; performing time stamping on the detection signal based on the conversion module to form multi-band time-domain scattering data, and generating corresponding multi-band OTDR measurement results by a processing module based on the multi-band time-domain scattering data.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a computer, cause the computer to perform the multi-band single-photon OTDR testing method of claim 9.

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