Patent Description:
According to a first aspect, there is provided a multiple front-end device based high speed optical time domain reflectometer (OTDR) acquisition system in accordance with any one of accompanying claims <NUM> to <NUM>,.

According to a second aspect, there is provided a method for multiple front-end device based high speed optical time domain reflectometer (OTDR) acquisition, the method according to any one of accompanying claims <NUM> to <NUM>.

Multiple front-end device based high speed OTDR acquisition systems, and methods for multiple front-end device based high speed OTDR acquisition are disclosed herein. The systems and methods disclosed herein provide for implementation of synchronous OTDR acquisitions, for example, by implementation of a plurality of OTDR measurements in parallel.

As disclosed herein, fiber optic cables may integrate a plurality of optical fibers. As data rate specifications increase, such specifications may result in an increase in a number of optical fibers in a fiber optic cable to therefore increase the capacity of the fiber optic cable. In some cases, measurement times associated with such optical fibers may be impacted by the number of optical fibers in the fiber optic cable. For example, an increase in a number of optical fibers in a fiber optic cable may result in relatively large overall measurement times associated with the fiber optic cable. This is because, in some cases, each optical fiber in a fiber optic cable may be sequentially measured. If the measurement time per optical fiber is reduced to reduce the overall measurement time for the fiber optic cable, such a reduction may negatively impact quality of the measurement results.

For example, <FIG> illustrates an OTDR and optical switch arrangement for measurement of a plurality of optical fibers in accordance with an example of the present disclosure.

With respect to <FIG>, a time to measure an optical fiber of a fiber optic cable may depend on factors such as characteristics of the optical specifications, expected performance, and performance of the measuring device. For example, measuring dynamics of the measuring device may need to cover a link budget with a margin that is sufficient for the expected performance. In the case of reflectometric measurement, the measuring device may be connected to one end of an optical fiber that is to be measured. The measurements may be made sequentially, for example, by using an optical switch, to measure one optical fiber after another of a fiber optic cable.

For example, as shown in <FIG>, with respect to automatic test configuration or fiber optic cable monitoring, an optical switch <NUM> may be utilized to time multiplex a measurement system. Thus, optical fibers <NUM> (e.g., fibers under test) may be tested sequentially. The optical switch <NUM> may be used to drive a single-port OTDR test signal to each test port onto which an optical fiber is connected. The optical switch <NUM> may be connected to a front end interface <NUM> of a fiber optic reflectometry system <NUM> (e.g., an OTDR). Further, the optical switch <NUM> may be connected to the optical fibers <NUM>. An optical stimulus <NUM> from the front-end interface <NUM> may be injected at <NUM> into an optical fiber, and a return signal <NUM> (e.g., backscattering, reflection, etc.) may be converted into an electrical signal. The electrical signal may be analyzed in an optical reflectometer main unit (ORMU) <NUM>.

The optical switch <NUM> may scan all of the optical fibers <NUM> with measurement parameters that may vary from fiber to fiber. A total measurement time may thus depend on each single fiber measurement time, and a number of fibers to be tested in a fiber optic cable. For example, an OTDR dynamic range may follow a 5LOG10(√N) law or <NUM>. 5LOG10(N) law, where N is the averaging number (or averaging time), to thus result in a gain of <NUM>. 75dB each time the acquisition time is doubled. For an example of a <NUM>-fiber sequential test, for a given total measurement time, the <NUM> fiber sequential test may need an improvement of more than 3dB of the measurement dynamics of the optical reflectometer main unit <NUM>. Additionally, switching time for the optical switch <NUM> may also be added. Thus, it is technically challenging to reduce measurement time with respect to optical fibers, without negatively impacting quality of the measurement results. It is also technically challenging to reduce measurement time with respect to optical fibers without increasing the performance specifications (and thus cost) of a measurement unit.

In order to address at least the aforementioned technical challenges, the systems and methods disclosed herein may implement synchronous OTDR acquisitions. For example, the systems and methods disclosed herein may implement a plurality of OTDR measurements in parallel. In some examples, the systems and methods disclosed herein may achieve high speed OTDR acquisitions based on a plurality of independent front-end devices (e.g., analog and optic front-end (A&OF-E) devices as disclosed herein). For example, the independent front-end devices may include optical heads that may be utilized as a front-end of an array of OTDRs.

According to examples disclosed herein, with respect to the independent front-end devices, such devices may include optic, optoelectronic, and electronic hardware, without any dedicated signal processing. The independent front-end devices may be utilized as a front-end of a plurality of fiber-optic measurement instruments.

According to examples disclosed herein, with respect to the independent front-end devices, the measurement instruments may control operation of at least one independent front-end device as an OTDR.

According to examples disclosed herein, with respect to the independent front-end devices, an array of the front-end devices may be utilized as part of parallel mono-directional or multi-directional measurement systems.

According to examples disclosed herein, with respect to the independent front-end devices, the measurement instrument may include a loss test set, and an array of the front-end devices may be used as part of parallel measurement systems.

According to examples disclosed herein, with respect to the independent front-end devices, the measurement instruments may control operation of at least one independent front-end device as a distributed fiber sensing interrogator.

<FIG> illustrate an architectural layout of a multiple front-end device based high speed OTDR acquisition system (hereinafter also referred to as "system <NUM>") in accordance with an example of the present disclosure.

Referring to <FIG>, with respect to optical fibers <NUM> of a fiber optic cable <NUM>, a plurality of analog and optic front-end (A&OF-E) devices <NUM> are implemented to simultaneously measure each optical fiber of the optical fibers <NUM>. As shown in <FIG>, each A&OF-E device (e.g., <NUM>(i)) may include a front-end driver <NUM>, an optical coupling system <NUM>, an optical receiver(s) <NUM>, a front-end power supply <NUM>, a front-end control unit <NUM>, a front-end receiver <NUM>, and optical source(s) <NUM>. Thus, each A&OF-E device of a set of <NUM>-to-n A&OF-E devices <NUM> include components of an optical head of a measuring instrument, as well as a minimum set of electronic components to allow the A&OF-E devices <NUM> to operate. By using a physical interface (e.g., a multiple front-end interface <NUM> as disclosed herein), the A&OF-E devices <NUM> are connected to corresponding ports (e.g., ports <NUM>-n) of the multiple front-end interface <NUM>. Further, by using a common electrical interface with the system <NUM>, the modularity of the <NUM>-to-n A&OF-E devices <NUM> may provide for the use of a specific A&OF-E device that provides specified measurements.

Referring to <FIG>, with respect to the aforementioned components of the A&OF-E devices <NUM>, the optical coupling system <NUM> may include a beam splitter, an independent wavelength coupler, an optical circulator or any other optical component to guide or switch an emission beam from optical source(s) <NUM> in the fiber, and couple the return signal to the optical receiver(s) <NUM>.

The optical coupling system <NUM> may include multiple ports for connecting multiple optical sources. The optical coupling system <NUM> may also include a plurality of ports on the optical receiver(s) side. In some applications, the optical coupling system <NUM> may include an optical filtering system for differentiating signals received at different wavelengths.

The front-end driver <NUM> may receive a control signal to control the optical source(s) <NUM>. In this regard, <FIG> shows an example in which the front-end driver <NUM> receives a signal to trigger an OTDR pulse. In other examples, this signal may trigger a sequence of a modulated signal.

The optical source(s) <NUM> may generate the modulated optical signals (e.g., pulse, wave train, or other modulations). These signals may be transmitted to a fiber via the optical coupling system <NUM>. Several optical sources may be combined to generate stimuli at different wavelengths or with different spectral widths, and/or with wavelength tunable devices.

The optical receiver(s) <NUM> convert the optical signal received from a fiber under test (e.g., one of the optical fibers <NUM>) via the optical coupling system <NUM>. Examples of optical receivers may include an avalanche photodiode in the case of a reflectometric application, a PIN photodiode in radiometric applications or telemetry signals, and other such photodiodes.

The front-end receiver <NUM> receives electric current from the optical receiver(s), and more precisely, from opto-electronic device(s), and converts this photocurrent into an electrical signal that may be used by the multiple front-end interface <NUM>. The conversion and pre-amplification of the current photocurrent from the photodiode may use a transimpedance amplifier for the current to voltage conversion. With respect to the electrical signal(s), the connection between the A&OF-E devices <NUM> and the multiple front-end interface <NUM> may use several lines and different technologies, such as symmetrical pairs, wireless channels or multiple serial data outputs (e.g., where the signal transmission from the A&OF-E devices <NUM> may be performed in a digital form). For example, in some cases when the signal line (e.g., wired or wireless) from an A&OF-E device may be relatively long or noisy, a serial analog to digital converter may be part of the A&OF-E devices and secure the transmission by using a digital signal. Thus, the "signal" indicated in <FIG> may represent an electrical raw signal from the front-end receiver <NUM> (sampled or not sampled).

As disclosed herein, multiple A&OF-E devices <NUM> are operated in parallel when configured for an application with the aid of the corresponding application software running on the measurement controller <NUM>. In this regard, the A & OF-E devices <NUM> and the other components of the system <NUM> may be designed to be software configurable.

The front-end power supply <NUM> locally generates the needed power supply for operation of an A&OF-E device. For example, the front-end power supply <NUM> may supply power to the various components of an A&OF-E device (e.g., the front-end driver <NUM>, the optical source(s) <NUM>, the optical receiver(s) <NUM>, the front-end receiver <NUM>, and the front-end control unit <NUM>). For example, in the case of an OTDR application, the front-end power supply <NUM> may generate an appropriate bias voltage of an avalanche photodiode forming part of the optical receiver(s) <NUM>. The front-end power supply <NUM> may also provide the appropriate voltage and current for the optical source(s) <NUM>.

The front-end control unit <NUM> may provide for control of the different elements of the A&OF-E devices <NUM>. The front-end control unit <NUM> may include data registers that include calibration parameters such as bias voltages of optic sources and optical receivers for different modes of operation, and also the status of the A&OF-E devices <NUM>.

For a measurement system block <NUM>, the sequential mode may be replaced by a parallel mode in which a plurality of the optical fibers <NUM> are tested simultaneously using a plurality of corresponding A&OF-E devices <NUM>. The A&OF-E devices <NUM> are connected to a measurement controller <NUM> (also referred to as shared main electronic part of measurement system) through the multiple front-end interface <NUM>. In this regard, the architecture of the system <NUM> may be divided with respect to the interfaces between the A&OF-E devices <NUM> and the multiple front-end interface <NUM>, and the A&OF-E devices <NUM> may include limited built-in functions. Other functions such as analog-to-digital conversion functions and application-specific data processing may be performed outside of the A&OF-E devices <NUM>. Thus, the measurement controller <NUM> may be used for multiple applications. Similarly, the multiple front-end interface <NUM> may include a plurality of interface connections that are configured for different types of A&OF-E devices <NUM>. Thus, different measurement systems may be constructed by selecting the appropriate A&OF-E device connected to the multiple front-end interface <NUM> which may convert different signals into digital data which may be processed by the measurement controller <NUM>. For example, sixteen A&OF-E devices <NUM> may be connected to the multiple front-end interface <NUM> which may allow the measurement controller <NUM> to process in parallel the data of sixteen reflectometric traces.

According to an example, the measurement controller <NUM> may be an OTDR. The measurement controller <NUM> may include measurement core features such as digital processing, data storage, power measurement, and an I/O interface. The measurement controller <NUM> may receive and process measurement raw data. The measurement controller <NUM> may include digital signal processing solutions, a memory space for data backup and results, and an interface to interact with various devices such as a screen, a printer, and a remote user. The separation between the measurement controller <NUM> and the multiple front-end interface <NUM> may be functional, and these two components may be physically implemented on the same electronic board or on different boards. However, with respect to the A&OF-E devices <NUM>, an array of <NUM> to n A&OF-E devices <NUM> may utilize a physical interface (e.g., connector pinout) between the interfaces <NUM> and the A&OF-E devices <NUM>. Thus, the multiple front-end interface <NUM> may include analog to digital conversion, and an A&OF-E interface.

Each A&OF-E device may be connected at one of the interfaces <NUM> to the multiple front-end interface <NUM>, which may include a trigger line for laser modulation, power supply connection, control lines, and the analog electrical signal from a preamplifier.

According to an example, components of the A&OF-E devices <NUM> may be limited to the components shown in <FIG>, without the addition of components such as a microprocessor and a data processor for the received signal.

According to an example, each A&OF-E device may work simultaneously with other A&OF-E devices at their own wavelengths, and may be synchronized with one or more of the other A&OF-E devices. In this regard, the A&OF-E devices <NUM> may provide for the simultaneous measurement of several optical fibers in parallel, and for the gain in measurement time per fiber. The A&OF-E devices <NUM> may be synchronized to perform parallel measurements.

For an example of an OTDR application, a pulse trigger may be shifted to avoid power consumption peak. The integration of elements specific to an OTDR in an A&OF-E device may limit the applicability of the A&OF-E device. Thus the A&OF-E devices <NUM> may provide for utilization for an OTDR application, as well as other applications that include the use of optical sources and receivers connected to the same optical fiber.

An A&OF-E device may represent an optical head interfacing a fiber under test (e.g., one of the optical fibers <NUM>) to the multiple front-end interface <NUM> to drive a plurality of other A&OF-E devices that may offer different features such as a continuous wave optical return loss (ORL) meter, OTDR, Echo meter, chromatic dispersion measurement, distributed fiber sensing measurements, or data link.

For example, as disclosed herein, the system <NUM> may include a set of <NUM> to n A&OF-E devices <NUM>, where each of the A&OF-E devices may be limited to including optical and optoelectronic components, and a minimum set of electrical components to provide for operation of the A&OF-E devices and for the exchange of data with other instruments of the system <NUM>. Yet further, as shown in <FIG>, by using a common physical interface such as the multiple front-end interface <NUM>, the connectable or pluggable A&OF-E devices may be used to build a plurality of fiber optic measurement instruments.

For example, referring to <FIG> illustrates an example of a configuration that may be used for the parallel measurement of several optical fibers using an array of <NUM> to n A&OF-E devices <NUM> for a reflectometric measurement application. The common interfaces <NUM> may allow different types of A&OF-E devices <NUM>, <NUM>, and <NUM> to be connected, depending on the need of the OTDR application. For example, the A&OF-E devices <NUM> may be equipped with optical or opto-electronic components of relatively low performance, the A&OF-E devices <NUM> may be equipped with relatively high-performance pulsed laser diodes to cover high dynamic measurement needs, etc. This flexibility may thus provide for the possibility to adjust the cost of the system <NUM>, and the cost of the <NUM> to n ports of the interfaces <NUM>. In this example, the measurement system block <NUM> may be formed by a combination of an array of AO&F-E devices and the shared part of measurement controller <NUM> and the multiple front-end interface <NUM>.

For the example of <FIG>, even a single A&OF-E device may be used in several modes. For example, the optical sources and the photodiodes may be used to generate a continuous optical signal, and to then measure optical return loss (e.g., to form an ORL meter). For example, the A&OF-E devices <NUM> may include a plurality of sources of different wavelengths to generate a Raman backscattering signal (e.g., Stokes, Anti-Stokes), which may be detected by one or two photodiodes dedicated to these wavelengths. The photocurrents may be transmitted to the front-end receiver <NUM>, and then the signals may be transmitted to the multiple front-end interface <NUM> to be digitalized. Temperature measurement may be processed by the front-end receiver <NUM> using the Raman backscatter data.

Chromatic dispersion may be performed with an A&OF-E device using either a broadband source and a tunable receiver, or using a tunable source and a broadband receiver (e.g., frequency scanning technique).

An A&OF-E device including a modulated laser may be used to transmit data, such as the measurement results on the optical fiber.

According to examples disclosed herein, the A&OF-E devices may facilitate implementation of a plurality of functions that may be synchronized together to build extended features such as parallel OTDR measurements, bidirectional parallel measurements, or any combinations of several A&OF-E devices <NUM>.

The A&OF-E devices <NUM> may share the same type of interfaces <NUM>. If the A&OF-E devices <NUM> are designed as pluggable units, any of the A&OF-E devices <NUM> may be plugged into any slot associated with the interfaces <NUM>. Even for use cases that include working at a same pulse with condition and distance sampling rate, implementation of the A&OF-E devices <NUM> as pluggable units may provide the capability of working at different wavelengths, with different pulse powers, and other different performance criteria. For example, the implementation of the A&OF-E devices <NUM> as pluggable units may be used when a second and shorter pulse width is needed for higher accuracy with respect to fault localization.

According to examples disclosed herein, with respect to the A&OF-E devices <NUM>, such devices may include optic, optoelectronic, and electronic hardware, without any dedicated signal processing. The A&OF-E devices <NUM> may be utilized as a front-end of a plurality of fiber-optic measurement instruments.

According to examples disclosed herein, with respect to the A&OF-E devices <NUM>, the measurement controller <NUM> controls operation of one or more A&OF-E device(s) of the plurality of A&OF-E devices <NUM> as an OTDR. In this regard, according to one example, the measurement controller <NUM> may control a single A&OF-E device that may make the system <NUM> equivalent to a single optical port instrument such as an OTDR with the possibility to interchange the optical front-end using different A&OF-E devices (e.g., user or factory configurable). According to another example, a single measurement controller <NUM> may control multiple A&OF-E devices <NUM>.

According to examples disclosed herein, with respect to the A&OF-E devices <NUM>, an array of the A&OF-E devices may be utilized as part of parallel mono-directional or multi-directional measurement systems. In this regard, bidirectional OTDR testing may represent a method of optical fiber characterization and loss testing that is performed from both ends of an optical fiber, for example, to provide increased accuracy and precision. For example, two measurement system blocks (e.g., the measurement system block <NUM>) may be connected on each end of a fiber optic cable. In the case of OTDR measurements on a multi-fiber cable or a multicore fiber, both ends of each fiber optic cable or each core may be connected to an A&OF-E device used as an OTDR A&OF-E device. In this regard, the optical source(s) <NUM> may be utilized in an OTDR mode such as a pulsed mode with the optical receiver(s) <NUM> configured for acquiring an OTDR signal from an optical fiber (e.g., Rayleigh backscatter signal plus signal from reflective events). With respect to the OTDR mode, according to an example of a configuration of the system <NUM>, most of the A&OF-E devices <NUM> may be designed to support OTDR mode, while other A&OF-E devices that are to operate as a continuous light source or as a power meter may support a loss test set mode where the optical source(s) <NUM> may be configured to operate in a continuous wave (CW) mode with an optical receiver using a dedicated bias voltage to perform CW optical power measurement. When using an A&OF-E device in an OTDR mode, an OTDR application software may operate on the measurement controller <NUM>. This configuration that includes both ends may provide bi-directional OTDR measurements.

According to examples disclosed herein, with respect to the A&OF-E devices <NUM>, the configuration of <FIG> and <FIG> may be operated as a loss test set, and an array of the A&OF-E devices may be used as part of parallel measurement systems.

According to examples disclosed herein, with respect to the A&OF-E devices <NUM>, the measurement controller <NUM> may control operation of one or more A&OF-E device(s) of the plurality of A&OF-E devices <NUM> as a distributed fiber sensing interrogator. In this regard, according to an example, the measurement controller <NUM> may control a single A&OF-E device to operate the system <NUM> as a single optical port fiber sensing instrument such as a distributed temperature sensing (DTS) interrogator with the possibility to interchange the optical front-end using different A&OF-E devices (e.g., user or factory configurable). According to an example, the A&OF-E devices <NUM> may be used to build a single-source DTS interrogator or a different type of interrogator that includes embedded optical and electrical hardware to implement a dual-source DTS. Alternatively, a single measurement controller <NUM> may control multiple A&OF devices <NUM> to sense multiple optical fibers in parallel, such as for using a DTS array for simultaneous fire detection.

<FIG> illustrate a flowchart of a method <NUM> for multiple front-end device based high speed OTDR acquisition, according to examples. The method <NUM> may be implemented on the system <NUM> described above with reference to <FIG> by way of example and not limitation. The method <NUM> may be practiced in other systems.

Referring to <FIG>, and <FIG>, and particularly <FIG>, at block <NUM>, the method <NUM> includes measuring, by specified analog and optic front-end devices of a plurality of analog and optic front-end devices, in parallel, light transmission with respect to specified optical fibers of a plurality of optical fibers.

At block <NUM>, the method <NUM> includes converting, by a front-end interface operatively connected to the plurality of analog and optic front-end devices, analog signals received from the specified analog and optic front-end devices to digital signals.

At block <NUM>, the method <NUM> includes controlling, by a measurement controller operatively connected to the front-end interface, operation of the plurality of analog and optic front-end devices.

At block <NUM>, the method <NUM> includes analyzing, by the measurement controller, based on the digital signals, a property (e.g., temperature variation, fiber bends, length, attenuation, joint loss, etc.) of the specified optical fibers.

<FIG> shows a computer system <NUM> that may be used with the examples described herein. The computer system may represent a platform that includes components that may be in a server or another computer system. The computer system <NUM> may be used as part of a platform for controllers of the system <NUM> (generally designated controller in <FIG>). The computer system <NUM> may execute, by a processor (e.g., a single or multiple processors) or other hardware processing circuit, the methods, functions and other processes described herein. These methods, functions and other processes may be embodied as machine readable instructions stored on a computer readable medium, which may be non-transitory, such as hardware storage devices (e.g., RAM (random access memory), ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), hard drives, and flash memory).

The computer system <NUM> may include a processor <NUM> that may implement or execute machine readable instructions performing some or all of the methods, functions and other processes described herein. Commands and data from the processor <NUM> may be communicated over a communication bus <NUM>. The computer system may also include a main memory <NUM>, such as a random access memory (RAM), where the machine readable instructions and data for the processor <NUM> may reside during runtime, and a secondary data storage <NUM>, which may be non-volatile and stores machine readable instructions and data. The memory and data storage are examples of computer readable mediums. The main memory <NUM> may include the controller (e.g., for the system <NUM>) including machine readable instructions residing in the main memory <NUM> during runtime and executed by the processor <NUM>.

The computer system <NUM> may include an input/output (I/O) device <NUM>, such as a keyboard, a mouse, a display, etc. The computer system may include a network interface <NUM> for connecting to a network. Other known electronic components may be added or substituted in the computer system.

Claim 1:
A multiple front-end device based high speed optical time domain reflectometer, OTDR, acquisition system (<NUM>) comprising:
a plurality of analog and optic front-end devices (<NUM>), wherein specified analog and optic front-end devices of the plurality of analog and optic front-end devices (<NUM>) are to measure, in parallel, light transmission with respect to specified optical fibers of a plurality of optical fibers (<NUM>);
a front-end interface (<NUM>) operatively connected to the plurality of analog and optic front-end devices (<NUM>), wherein the front-end interface (<NUM>) is to convert analog signals received from the specified analog and optic front-end devices(<NUM>) to digital signals;
a measurement controller (<NUM>) operatively connected to the front-end interface (<NUM>) to
control operation of the plurality of analog and optic front-end devices (<NUM>), and
analyze, based on the digital signals, at least one property of the specified optical fibers (<NUM>); and wherein each analog and optic front-end device of the plurality of analog and optic front-end devices (<NUM>) includes a front-end receiver (<NUM>) to:
receive a photocurrent from an optical receiver (<NUM>) that receives a return signal from a corresponding optical fiber of the specified optical fibers (<NUM>); and
convert the photocurrent to an electrical signal for analysis of the at least one property.