Fiber Optic Sensors

光纤传感器

便携式和机架安装式选件中行业领先的模块化光纤传感器

VIAVI 提供了唯一的完全便携式 DTS 和 DTSS 解决方案,其中也包含了传统的 OTDR。大多数温度和应变传感设备都只能安装在机架上。我们的光纤传感解决方案采用模块化设计和电池供电方式,并可与 MTS-8000 可扩展综合测试平台或结合 OTU-8000 单元的 VIAVI ONMSi 解决方案兼容。OTU-8000 是一种模块化的光学测试头,其中包含 OTDR、布里渊 OTDR、瑞利 OTDR 和开关,可通过自动化例程对多条光纤进行监控。

VIAVI 提供什么类型的光纤传感询问器?

VIAVI 光纤传感产品组合包括:

  • 基于瑞利 OTDR 技术的 DTS(分布式温度传感)
  • 基于布里渊 OTDR 技术的 DTSS(分布式温度和应变传感)

如何实现对基础设施的定期检测?

使用包含 DTS 和 DTSS 模块的便携式设备(例如 VIAVI MTS-8000 平台),技术人员可以前往现场并对光纤执行现场测量。或者,通过将 ONMSi机架安装式 OTU(光学测试设备)与 DTS 或 DTSS 结合使用,可以通过定期跟踪(设置为在初始参考跟踪发生变化时报警)来 监控 光纤。

与传统机电传感器相比,使用分布式光纤传感器能够带来怎样的经济效益?

在用作安装和用作数据点丰富来源时,光纤传感器便宜很多,并且所需的人工更少。线缆中的光纤构成分布式传感器,这种材料很便宜,重量轻,并且可轻松连接或嵌入到所测试的对象。 

光纤是高度可靠的分布式传感器,它不需要恒定电流来生成数据,并且不会受到电磁和无线电频率干扰。在过去,沉重并且在安装时需要大量人力的有线电气式传感器一直是用于获取应变或温度数据的主要数据源。

机电传感器可能会跌落、容易被侵入且成本高昂,并且,它们还需要电源。在没有现成电源或者存在腐蚀、振动或 EMI 问题的地点,机电传感器不实用。电气和无线电噪声的进出可能会使其测量数据失真。经济高效的光纤传感器监控最适合用于需要安全监控的桥梁,在光纤传感器监控中,光纤可以嵌入或追溯性地连接到桥梁,在桥梁实际出现故障之前检测出应变和故障风险。只要光纤未过度弯曲,就能以正弦波形状安装光纤,从而在表面上形成更多的数据点。OTDR 可以检测微弯和宏弯,并且,如果应用中需要略微拉紧的光纤,则可用于在安装光纤传感器时优化光纤应变和弯曲。

光纤传感器有什么优势,可以用于获得哪些数据类型?

光纤传感器可通过光时域反射仪 (OTDR) 提供多种类型的数据,包括指示移动的声学、应变、温度和光传输特性数据,或者光纤中的弯曲和断裂。可以在整个光纤范围内获取此数据,而不局限于分散和间歇性放置的传感器位点。例如,使用 OTDR 来测量这些项目将可揭示出长跨距光纤范围内的温度梯度变化。用户还可以看到以光纤伸长表示的应变的开始和结束位置。远程通信中需要避免应变,因此对应变进行测量可以保护网络,并且可以提前缓解和修复线缆应变。如果用户想要对桥梁进行监控,光纤传感器上的应变可以指示桥梁的运动,例如下垂、下沉或桥板分离所导致的压力。

假设要对需要非常特定温度范围的建筑(例如数据中心、核电站或血库贮存设施)的温度进行测量。 传统的电气式恒温传感器放置在若干位置,并定期获取不连续点的读数。电子式温度传感器非常昂贵,而且需要持续供电。如果测量位置缺少传感器,或者传感器由于断电、极端温度或 EMI 干扰而出现故障,会发生什么情况? 温度未以最佳方式加以控制,因此产生了热点或冷点。由一条或多条光缆构成的光纤传感器网可以遍布整个建筑,从而可以在连续的位置获取读数。光纤网可提供更多数据点,以更低的成本实现更大的覆盖范围,并且可靠性更高。只需要激光器 OTDR 发出的光脉冲便可询问光纤传感器,并且在断电的情况下可以通过电池对设备进行超过一天的供电。

光纤传感器有哪些变革性的应用?

数据和电信光缆监控:

全球各地的通信电缆都布置在崎岖荒凉的地下、海底和高空环境中,在这样的环境中,冰、风、地球运动/侵蚀、波浪、破坏行为以及人为错误都会不断使线缆产生应变或者断裂,从而导致服务中断和服务降级。在安装过程中,有时也会意外地使线缆产生应变。一旦发生过度应变,线缆就面临断裂的风险,并且线缆的寿命也会从 35-40 年大幅减少到仅仅数月。

Fiber Optic Sensors

Fiber Optic Sensors

长距离线缆和海底线缆非常重要,而在出现恶劣天气或处于偏僻、危险的地势中时,维修非常困难。通过使用光纤传感器完成的分布式应变传感,网络线缆所有者将能在安装时对光纤进行测试,然后监测暗纤是否有过度应变风险,并在维修过程中监测应变的变化,从而减少破损。毛里塔尼亚最近遭受了一次海底线缆断裂事故,造成整个网络与互联网断开长达两天。导致这次事故的原因是一艘拖网渔船将非洲海岸到欧洲的线缆从海底拔起并拉断。假如对此线缆进行了应变监控,在线缆被拔起拉断之前就会触发警报。如果线缆最终断裂,经典的瑞利 OTDR 可在一米的误差范围内找到断裂处,从而缩短运行中断时间。

假设一条高空线缆负冰过重。网络运营商可以对线缆进行监控,并安排工作人员对有需要的网段进行除冰,从而防止产生过度应变。发生应变事件后,可以依据 MAT 容差测量结果对线缆进行测试,从而确定更换优先级。可提供便携式 DTSS 光纤传感器 OTDR 和机架安装式光纤询问 OTDR。 

Broken aerial cable preventable with fiber optic sensors

通信线缆维修和保险退款: 

线缆断裂的最常见原因是施工挖掘(也称为挖掘机衰减)。 通常在找到断裂后,会在断裂位置对线缆进行接合或连接。但是,这只能暂时解决问题,因为当挖掘机将线缆从地下拉出时,应变已经损坏了断裂位置两侧的数米线缆。 

Backhoe repairing broken cable

线缆在重新安装时可能会再次断裂,或者过度损坏导致性能严重降低,以至于无法提供充分的服务。重复进行维修成本高昂,并且导致服务多次中断。通过在出现断裂时在线缆的上下两个方向上使用光纤传感器 OTDR 进行分布式应变测量,技术人员可以提供科学证据来精确地展示应更换线缆的哪些部分。可以使用此证据来向责任方追讨损坏费用。它可防止后续重复派遣维修人员并造成客户服务中断,也可避免不必要地维修没有遭受应变损坏的正常线缆部分。

管道或堤坝泄漏检测:

在石油行业、化工行业、食品行业、废品行业和水利行业中,使用管道运送各种类型昂贵并且可能有腐蚀性的物质。溢漏、造成污染物进入管道的泄漏或者盗窃可能会导致灾难性的问题。通过测量管道沿线光纤的温度和应变,可以实现管道监控。 同样,也可以用类似的方式对堤坝进行监控。如果光纤的温度或者应变或光反射特性发生大幅变化,则疑似存在泄漏。温度变化可能指示泄漏或偷盗,应变可能指示由于意外运动而存在断裂的风险。并且,通过使用传统的光反射瑞利散射 OTDR 分析可以在一米的误差范围内确定问题的位置。在机架安装式 OTDR 监控解决方案中,可以使用针对应变、温度和光反射的光询问器组合来持续监控连接到管道的光纤传感器。光纤传感器提供准确的检测,从而可快速完成关闭、检测和维修过程。

Pipeline leak detection possible with a fiber sensor

输电线热点检测:

电力传输设备上的电热点会造成危及生命的火灾风险和基础设施损坏。 美国加利福尼亚州最近就发生了这样一个例子,当时,一处电热点或掉落的电力电缆可能引发了一场森林火灾。这场火灾造成了生命和财产损失,涉事电力公司正面临着诉讼和破产风险。

使用分布式温度传感 (DTS) 实现的远程光纤传感是监控此类问题唯一经济的方式,与这种灾难性事件的代价相比,成本要低廉得多。光纤放置在输电线路沿线,用于对线路进行远程监控。 当光纤传感器系统检测到温度上升、应变或可能表示线路掉落的弯曲时,便会触发警报。通过将该系统与瑞利 OTDR 分析结合使用,可以将参考轨线与恒定的定期轨线进行比较,从而在光纤位置发生渐变或突变时确定精确位置。警报可以触发紧急断电和对输电线路的调查。由于使用光纤传感器的光纤分析不受 EMI 的影响,因此在这种高 EMI 环境中,它是理想的数据来源。

Hotspots and leakage

 

详细了解光纤传感、  光纤测试 和光纤监控

产品

ONMSi Remote Fiber Test System (RFTS)

ONMSi 远程光纤测试系统 (RFTS)

用于核心、城域、接入和 FTTH 网络的 ONMSi 光网络管理系统。

MTS-8000 平台

MTS-8000 是世界上用于下一代高速网络部署(40G 和100 G)的扩展性最好的测试平台。它是一个多应用测试平台,支持物理、光学和传输/以太网测试功能。
Fiber Test Head (FTH-9000)

FTH-9000

用于远程光纤测试的自适应光纤测试头 (FTH) FTH-9000,带 OTDR 和开关选项
DTSS on the T-BERD/MTS-8000 platform

DTSS B-OTDR for T-BERD/MTS-8000 Platform

The portable DTSS on the T-BERD/MTS-8000 platform brings new DTSS technology to the field in a uniquely portable and high powered combination. This product can also be provided in a rack-mounted optical test unit within an OTU-8000 to be combined with ONMSi for a permanent fiber monitoring solution.
OTU-8000 Optical Test Unit

OTU-8000 OTDR 测试系统

使用机架安装式自动化 OTDR 测试自动进行光网络监控,该设备提供了各种各样的 OTDR 模块,可进行传统 OTDR 轨线测量,以及 DTS 和 DTSS(分布式温度和压力)测量。

What Type of Fiber Optic Sensing Interrogators Does VIAVI Offer?

The VIAVI fiber sensing portfolio includes:

  • DTS (Distributed Temperature Sensing) based on Raman OTDR technology
  • DTSS (Distributed Temperature and Strain Sensing) based on Brillouin OTDR technology

What is a Fiber Optic Strain Sensor?

A Fiber Optic Strain Sensor, also known as an optical strain gauge, is an optical fiber used to detect or sense strain through a process known as distributed strain sensing using a specialized OTDR (Optical Time Domain Reflectometer). These sensors are used to measure light changes in the sensor to detect strain on a fiber as areas along the glass fiber stretch producing changes to the glass until it will eventually break under excessive strain. Unlike traditional electrical strain gauges, a passive fiber optic strain sensor does not require constant electrification and is immune to electro-magnetic interference, which is experienced as noise in an electrical strain gauge system. Such noise can render measurements unreadable.

Due to this advantage, they are less expensive to operate and can be used in many harsh physical environments as reliable measurement devices with extraordinary sensitivity to strain change. Detect strain by transmitting a light pulse down the fiber to measure the strain on the glass. These types of measurements can be taken periodically with a portable DTSS (Distributed Temperature and Strain Sensor) OTDR during a field measurement trip or in an automated routine using a permanent, rack-mounted DTSS OTDR. The optical fiber is light weight, inexpensive and thorough coverage can be achieved by attaching the fiber to the device under test in multiple locations.

A fiber optic strain sensor can be used to sense strain in diverse locations such as along a pipeline, on a telecommunications cable, in the earth, along a bridge, or large windmill to secure infrastructure, human life, and prevent environmental damage. All sound measurement processes will establish a baseline of strain upon installation of the fiber optic strain sensor and measure change over time, allowing an automatic alarm to trigger notification of risk should a specified tolerance threshold be breached.

How Can Infrastructure Be Inspected Periodically?

Using a portable, such as the VIAVI T-BERD/MTS-8000 platform with a DTS or DTSS module, a technician can go out into the field and conduct field measurements on fibers. Alternatively, using ONMSi and a rack-mounted OTU (Optical Test Unit) with a DTS or a DTSS monitors fibers using periodic traces that are set to alarm if there is a change from the beginning reference trace.

What are the Economic Benefits of Using Distributed Fiber Optic Sensors Over Traditional Electro-Mechanical Sensors?

Fiber optic sensors are much less expensive and less labor intensive to install and utilize as a data point rich source. The fibers in the cable make up the distributed sensor and this material is inexpensive, lightweight and easy to attach or embed to an object under test.

Fibers are highly-reliable distributed sensors that do not require constant electrical current to produce data, and they are immune to electro-magnetic and radio-frequency interference. Historically, heavy, wired, electrified sensors that are labor intensive to install have been the main data source for obtaining strain or temperature data.

Electro-mechanical sensors can fall off, be intrusive and cost prohibitive and they require a power source. In locations where power is not readily available or, corrosion, vibration or EMI is a problem, they are not practical. Electrical and radio noise ingress or egress distorts their measurement data. A bridge that needs safety monitoring is a prime candidate for cost-effective fiber optic sensor monitoring, in which the fibers can be embedded or retro-actively attached to the bridge to detect strain and risk of failure before the bridge actually fails. As long as the fiber is not bent excessively, the fiber can be installed in a sine wave shape to allow for more data points across a surface. An OTDR can detect micro and macro bends and can be used to optimize the fiber strain and bends at the installation of the fiber sensor if a slightly strained fiber is required in the application.

What Advantages and Data Types can be Obtained from Fiber Optic Sensors?

Fiber optic sensors can provide multiple types of data through optical time domain reflectometry (OTDR) including data on the acoustics, strain, temperature and light transmission properties that indicate movement, or bends and breaks in the fiber. This data can be provided across the entire length of the fiber(s) instead of being limited to discrete and intermittently placed sensor sites. For example, using an OTDR to measure these items will reveal where the temperature changes by gradient across a long fiber span. One can also see where strain in the form of fiber elongation begins and ends. In telecommunications, strain needs to be avoided and thus measuring this protects the network and allows proactive cable strain mitigation and repair. If one wants to monitor a bridge, the strain on the fiber sensor can indicate movement of the bridge such as sagging, sinking or stress caused by separation of the bridge plates.

Consider measuring temperature throughout a building that requires a very specific temperature range, such as a data center, nuclear plant, or blood bank storage facility. Traditional electrified thermostatic sensors are placed in several locations and take periodic discrete point readings. Electronic temperature sensors are expensive and requires constant electrification. What happens when the location is missing a sensor or the sensor fails due to power loss, temperature extremes, or EMI interference? The temperature is not optimally regulated creating a hot or a cold spot. A fiber optic sensor net in the form of one or more fiber cables can be run throughout the building to obtain readings across continuous locations. The fiber net can provide more data points for better coverage at a lower cost with higher reliability. A pulse of light emitted by a laser OTDR is all that is required to interrogate the fiber sensor and the device can be powered by a battery in case of a power outage for more than a day.

 

What are some game-changing applications of fiber optic sensors?

Data and Telecommunications Fiber Cable Monitoring:

Communications cables are placed all over the world in rugged, inhospitable subterranean, submarine and aerial environments where ice, wind, earth movement/erosion, waves, vandalism, and human error constantly strain or break the cables, causing both service outages and service degradation. Cables are sometimes strained accidentally during installation. Once excessively strained, the cable is at risk of breaking and the lifespan of the cable is dramatically reduced from 35-40 years to potentially just months.

Fiber Optic Sensors

Fiber Optic Sensors

Long-haul and submarine cables are mission critical but are difficult to service in inclement weather or remote, dangerous terrain. Distributed strain sensing with a fiber optic sensor will allow a network cable owner to test the fiber at installation, and then monitor a dark fiber for excessive strain risk and changes in strain while in service to mitigate breakage. Mauritania recently experienced a break in the submarine cable that disconnected the entire network from the internet for two days. This was caused when a trawler lifted the African Coast to Europe cable off the sea floor and broke it. Had this cable been monitored for strain, an alarm would have triggered as the cable was being pulled before it broke. If it did end up breaking, a classic Rayleigh OTDR could have located the break within one meter, thus reducing the outage time.

Consider an aerial cable bearing an excessive ice load. The network operator can monitor the cables and locate network segments where staff should perform ice removal to prevent excessive strain. After a strain event has occurred, the cable can be tested against MAT tolerance measurements to be prioritized for replacement. Both portable DTSS fiber optic sensor OTDRs and rack-mounted fiber interrogation OTDRs are available. 

Broken aerial cable preventable with fiber optic sensors

Communication Cable Repair and Insurance Coverage Chargeback: 

The most common cause of cable breakage is due to construction digging, aka backhoe attenuation. Often when the break is located, the cable is spliced or connectorized at the break location. However, this may only resolve the problem temporarily because the strain has damaged many meters of cable on both sides of the break when the backhoe pulled the cable out of the ground.

Backhoe repairing broken cable

The cable may break again as it is re-installed or become so degraded that it is too damaged to provide adequate service. Repeat repairs are expensive and cause additional service outages. By taking distributed strain measurements with a fiber optic sensor OTDR in both directions up and down the cable when the break occurs, the technician can provide scientific evidence to demonstrate precisely which section(s) of cable should be replaced. This evidence can be used to charge the responsible party for the cost of the damage. It prevents further repeat repair dispatches and service disruption to customers as well as unnecessary repairs on good cable sections that have not experienced strain damage.

Pipeline or Dam Leak Detection:

Pipelines carry all types of expensive and potentially caustic materials in the oil, chemical, food, waste and water industries. A spill, leak that causes contamination into the pipeline, or theft can cause catastrophic problems. Pipeline monitoring is accomplished by measuring fibers for temperature and strain along the pipeline. Likewise, a dam or dike can be monitored similarly. A leak is suspected if there is a dramatic change in temperature, or the strain or light reflectance properties of the fiber. Temperature can be indicative of a leak or tap, strain is indicative of risk of breakage due to unexpected movement, and the problem can be located within a meter by using classic light reflectance Rayleigh scattering OTDR analysis. A combination optical interrogator, for strain, temperature and light reflectance can be used in a rack-mounted OTDR monitoring solution to continually monitor the fiber sensors attached to the pipeline. Fiber optic sensors provide accurate detection allowing shutdown, inspection, and repairs to be done quickly.

Pipeline leak detection possible with a fiber sensor

Powerline Hot Spot Detection:

Electrical hot spots on power transmission plants cause life-threatening fire risk and infrastructure damage. A recent example may have happened in California, USA when an electrical hot spot or downed electric cable may have ignited a forest fire. Lives and property were lost and now the utility is facing lawsuits and bankruptcy.

Remote fiber sensing using distributed temperature sensing (DTS) is the only economical way to monitor such problems and is much less expensive than the cost of such a catastrophic event. A fiber is placed along the transmission line to remotely monitor the line. An alarm is triggered when the fiber optic sensor system detects a rise in temperature, a strain or bend that can indicate a line fall. By pairing it with Rayleigh OTDR analysis, a precise location can be determined when there is either a gradual or abrupt shift in the fiber position by comparing a reference trace to a constant, periodic trace. The alarm can trigger an emergency power shutdown and investigation of the transmission lines. Because the fiber analysis using a fiber optic sensor is immune to EMI, it is the ideal source of data in this high EMI environment.

Hotspots and leakage

 

Learn more about Fiber Sensing,  Fiber Testing and Fiber Monitoring.

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