Category Archives: passive optical components

Getting More Benefits From Sensing Fiber Optic Cables

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Sensing fiber optic cable is a type of optical cable that can monitor temperature, strain, acoustics and pressure. They are suitable for a wide range of applications like fire detection, vibration monitoring, industrial plant temperature sensing, temperature gradients in soil, pipeline leak and intrusion detection. Although these cables are built based on standard fiber optic cable which only operates to 85℃, the highest working temperature of them is up to 700℃. Before knowing what benefits that sensing fiber optic cable could bring to our life, let’s figure out the common types of sensing optical cable at first.

PBT Tube Temperature Sensing Optical Cable

The major difference of this optical cable is that the bare fiber inside is protected by a PBT tube. Except that, it is comprised of fiber, oil, aramid yarn and a sheath which can be made of different materials such as PVC, LSZH, PU and PE. With the unique structure, this sensing fiber optic cable is suitable for applications in subway systems, tunnels and fire protection industries to sense temperature and pressure, helping to prevent disasters and accidents.

PBT tube temperature sensing fiber optic cable

Armored Temperature Detecting Sensor Cable

Armored fiber optic cable is very common in optical communication. However, this kind of armored sensing cable is a little different. They are strengthened by both SUS spring tube and SUS braiding, which bring them very good mechanical performance of tensile resistance and pressure resistance. Therefore, these cables are widely applied to fire detecting, building health detecting and temperature detecting.

Teflon Sheathed Sensor Cable

Teflon, or PTFE (Poly tetra fluoroethylene) is used in a wide variety of high temperature applications like gas turbine and high voltage gas ignition wires due to its higher melting point. Besides, the aramid yarn and stainless steel braiding ensure good crush-resistant performance and the tensile strength of the cable. With all these characteristics, Teflon sheathed sensor cable is a good choice for high temperature resistant environment and fiber temperature sensing systems.

Teflon sheathed sensing fiber optic cable

Seamless Tube Temperature Sensing Cable

This armored fiber optic cable consists of bare fiber, oil, seamless stainless steel tube and an outer jacket. This structure brings a high tensile strength, crush resistance, a compact size and an unmatched steel performance to this fiber cable. And it features a simple structure and small size, but providing prominent transmission performance. With this sensor cable, some accidents that frequently occur in places such as tanks and mines can be avoided.

Copper Braid Armored Sensor Cable

As its name shows, there is a copper braiding around the outer jacket of this sensing cable. Copper braid is made from weaving together strands of copper wire. The flexibility of the braid is determined by the diameter of the copper wire. The smaller the wire, the greater the flexibility. And the larger the volume occupied by the braid, the more expensive the braid becomes. Apart from the copper braiding, there are stainless steel flexible tube and stainless steel braiding outside the bare fiber, which make the cable more suitable for outdoor optical fiber communication and optical fiber sensor. With the copper braiding structure, the special cable can prevent the external electromagnetic field on internal invasion, reducing its optical transmission loss.

Copper braid armored sensing fiber optic cable

Silica Gel Sensing Optical Cable

Unlike copper braid armored sensor cable, the silica gel sensing optical cable has a very simple structure, including bare fiber, Teflon tube, armored yarn and silicone jacket. As have mentioned above, Teflon is a high performance alternative insulation. With the silica gel that is another kind of good insulation material, both of them make this sensing fiber optic cable an ideal solution for high temperature resistant and high voltage environment. It can work normally even in the 250℃ high temperature environment or 6kv high voltage environment without affecting optical signals’ transmission.

Summary

The deployment of sensing fiber optic cables brings us lots of benefits in various applications. They can be applied in downhole to monitor temperatures either as DTS or datacom links to sensors; they can be deployed in power distribution networks to monitor performance of power cable systems; they can be attached to pipelines for temperature data that’s available on demand. This post introduces six kinds of sensing fiber optic cable. All of them are available on FS.COM. Welcome to contact us via sales@fs.com.

Optical Switches Overview

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An optical switch is a device that can selectively switch light signals that run through in optical fibers or integrated optical circuits from one circuit to another. That is to say, optical switches can transfer light signals between different channels in communication networks. As the growing popularity of Internet and telephone, greater quantities of data managed by communication networks also expanded. Optical switching technology provides a perfect solution to fully exploit capacity of optical systems. The main focus of this post is to introduce basics of optical switches in optical communication.

optical-switches

Working Principles & Functions of Optical Switches

As we all know, when a light signal runs through from one computer to another in fiber optic networks, it may be required to move the signal between different fiber paths. To accomplish this, a switch is required to transfer the signal with a minimum loss. Optical switch is a technology needed. The optical switch we often see is operated by mechanical method which just moves fiber or other bulk optic components. But they can offer unprecedented high stability and unmatched low cost performance.

Optical switches are mainly deployed in establishing the light path. They feature scalability and highly reliable switching capacity. Following are the major functions that optical switches bear in optical cross networks.

  • Protection. Sometimes a failure of some single point can cause the whole network breaking down. And the protection switching is to protect the transmission data, which can avoid network fault before finding the failure causes.
  • Optical add/drop multiplexing. Optical switches must be equipped with the capability that can add or delete the wave channels without any electronic processing. This kind of optical switches is also called wavelength selective switches.
  • Optical spectral monitoring. Optical spectral monitoring is a network management operations. In this process, operators receive a small portion of optically tapped signal for monitoring power level, wavelength accuracy and optical cross talk.
Common Types of Optical Switches

As data requirements grow, the traditional electrical switches no longer meet people’s demand. There are two major types of optical switches on the market: opto-mechanical optical switches and MEMS (Micro-electromechanical Systems) optical switches.

Opto-Mechanical Optical Switches

Opto-mechanical optical switch is an old type of switches but the most widely used one. It can produce different optical path selections out of a plurality of optical path sections that are oriented in different spatial directions. Hence opto-mechanical optical switches can be used in multi-channel optical power monitoring, optical local area networks, switching multiple laser sources or optical receivers in Ethernet networks. They are also very useful in optical fiber, components or systems testing and measurement, as well as applications in multi-point fiber sensor systems. Generally, according to the number of redirecting signals, opto-mechanical optical switches have different configurations such as 1×1, 1×2, 1×4, 1×16, etc. In simple terms, the 1×8 opto-mechanical optical switch module connects optical channels by redirecting an 1 incoming optical signal into a selected signal from 8 output fibers. This kind of optical switches can achieve excellent reliability, insertion loss, and cross talk.

opto-mechanical-optical-switches

MEMS Optical Switches

MEMS optical switches use a micro-mirror to reflect a light beam. And the direction that the light beam is reflected can be changed by adjusting the angle of the mirror, which allows the input light to be connected to any out port. It is a compact optical switch which connects optical channels by redirecting incoming optical signals into the selected output fibers. And the switching state is highly stable against environmental variations of temperature and vibration due to its unique design. In some degree MEMS optical switch can be considered as a subcategory of opto-mechanical switches. But it is distinguished from opto-mechanical switches in many aspects such as the characteristics, performance and reliability. The most obvious is the opto-mechanical switch has more bulk compared to other alternatives, but the MEMS switch overcomes this. Besides, MEMS optical switches also have different configurations such as 1×8, 1×12, 1×16, etc.

1x8-mems-optical-switch

Summary

As the increasing growth of high speed transmission demand for networks, optical networks have become the most cost-effective solution. Optical switches play a vital role in today’s optical network system. They can offer users significant power, space and cost savings. Now different optical switches are available on the market, so you can choose a suitable one based on your requirements.

Fiberstore Passive Optical Components Solution

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Passive optical components market is propelled by the accelerating bandwidth requirements coupled with the growth of passive optical network (PON). Usage of passive optical components to obtain energy efficient network solutions is gaining popularity. This article will introduce some Fiberstore passive optical components.

Optical Attenuators: an optical attenuator is a device that is used to reduce the power level of an optical signal. Optical attenuators are commonly used in fiber optic communications, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels.

optical attenuators

Optical Circulator: an optical circulator is a multi-port (minimum three ports) non-reciprocal passive component. The function of an optical circulator is similar to that of a microwave circulator — to transmit a light wave from one port to the next sequential port with a maximum intensity, but at the same time to block any light transmission from one port to the previous port.

optical circulator

Fiber Collimator: a fiber collimator is a device for collimating the light coming from a fiber, or for launching collimated light into the fiber. It is used to expand and collimate the output light at the fiber end, or to couple light beams between two fibers. Both single-mode fiber collimators and multimode fiber collimators are available.

fiber collimator

Optical Isolator: an optical isolator is a passive optical component that allows light to propagate in only one direction. Optical isolators are typically used to protect light sources from back reflections or signals that can cause instabilities and damage. The operation of optical isolators depends on the Faraday effect, which is used in the main component, the Faraday rotator.

optical isolator

Fiber Optic Sensor: a fiber optic sensor is a sensor that uses optical fiber either as the sensing element (intrinsic sensors), or as a means of relaying signals from a remote sensor to the electronics that process the signals (extrinsic sensors). Fiber optic sensors are immune to electromagnetic interference, and do not conduct electricity so they can be used in places where there is high voltage electricity or flammable material such as jet fuel.

fiber optic sensor

Pump Combiner: a pump combiner is a passive optical component built based on fused biconical taper (FBT) technique. Pump combiners are widely used in fiber laser, fiber amplifier, high power EDFA, biomedical and sensor system etc. Three types of pump combiners are available: Nx1 Multimode Pump Combiner, (N+1)x1 Multimode Pump and Signal Combiner, PM(N+1)x1 PM Pump and Signal Combiner.

pump combiner

Polarization Components: polarization is the state of the e-vector orientation. Polarization components are used to isolate and transmit a single state of polarized light while absorbing, reflecting, and deviating light with the orthogonal state of polarization. Polarization components can be utilized in high power optical amplifiers and optical transmission system, test and measurement.

polarization components

Fiberstore has all of the above passive optical components with high quality and reasonable price. You can select excellent passive optical components or other optical products for your network at www.fs.com.

Passive Optical Network – a Superior Network Solution

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With the explosive growth of Internet, the introduction of a broadband access network based on fiber-to-the-office (FTTO) and fiber-to-the-home (FTTH) has been triggered. Under this circumstance, access and metro networks should be scalable in terms of capacity and accommodation as well as flexible with regard to physical topology. Passive optical network (PON), one class of fiber access system, can deal with the various demands.

Definition

A passive optical network (PON) is a telecommunication network that uses point-to-multipoint fiber to the end-points in which unpowered optical splitters are used to enable a single optical fiber to serve multiple end-points. It consists of an optical line terminal (OLT) at the service provider’s central office and a number of optical network units (ONUs) or optical network terminals (ONTs), near end users (see the figure below). PON takes advantages of wavelength division multiplexing (WDM) and uses one optical wavelength for upstream traffic while another for downstream traffic on a single-mode fiber. The upstream signals are combined at the splitters by using a multiple access protocol (time division multiple access). The downstream signals are directed to multiple users by using passive optical splitter technology.

passive optical network
Advantages

Signals in a shared fiber architecture can be split out using two methods. One is active Ethernet (AE), with which the individual signals are split out using electronic equipment near the subscriber. The other one is PON, in which the signals are replicated passively by the splitter. Compared with AE, a network based on a PON system is more superior. The advantages of PON are as below.

PON incurs lower capital expenditures because it has no electronic components in the field. Also PON lowers the operational expenditures as there is no need for the operators to provide and monitor electrical power in the field or maintain backup batteries. Besides, a PON has a higher reliability because in the PON outside plant there are no electronic components which are prone to failure. Additionally, one of the most crucial features of a PON-based access network is its signal rate and format transparency. It is much simpler for a PON to upgrade to higher bit rates. Both AE and PON require upgraded electronics in the central office (CO) and customer premises, but unlike AE, PON does not need to upgrade in the outside plant as the passive splitters are agnostic to PON speed. Lastly, a PON solution has the ability to span long distances without degrading performance. The low-loss characteristics of single-mode fiber enable PON to support a maximum physical reach of 20 kilometers.

Applications

There are some applications for which PON is well suited, such as fiber-to-the-home (FTTH) delivery of voice, Internet data, and cable access broadband video. More specifically, PON is used when the applications require anticipated system to upgrade to high-security areas or where the rerouting of cable may be difficult. Or in the cases that installations involving widely dispersed nodes require long runs of fiber. And PON is utilized for the projects where costs, especially initial deployment costs, are a key concern. At the same time, using PON can help user bandwidth to be adequately managed.

By reading the above illustration, have you got a basic understanding about the passive optical network? Fiberstore, a professional manufacturer and supplier in the optical industry, has many high-quality PON products including PON splitters, optical network units and optical line terminal. Choosing a PON product in Fiberstore can help to deploy your network more efficiently.

Introduction to Fiber Optic Sensor

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In recent years, fiber optic sensor has been deployed successfully in the supervision of structures. Because it is immune to electromagnetic interference and can handle extreme conditions, so it is gaining popularity as the sensor of choice for many industries. Fiber optic sensor is a sensing device that converts light rays into electronic signals. It is usually used for measuring physical quantities such as temperature, pressure, strain, voltages and acceleration etc. This blog is to introduce fiber optic sensor’s classification, characteristics and applications.

Classification

Fiber optic sensor can be mainly classified by sensing location, operating principle and applications. Depending on location of sensor, there are intrinsic and extrinsic fiber optic sensors. Considering the operating principle and demodulation technique, fiber optic sensors can be further divided into intensity, phase, frequency and polarization sensors. Based on application, fiber optic sensors can be classified in physical, chemical, bio-chemical sensors.

Characteristics
Fiber optic sensor offers unique characteristics that make it very popular and sometimes become the only viable sensing solution. Some inherent characteristics of fiber optic sensor are shown as following:

  • Harsh environment stability to strong electromagnetic interference immunity, high temperature and chemical corrosion, as well as high pressure and high voltage etc.
  • Very small size, passive and low power.
  • Excellent performance such as high sensitivity and wide bandwidth.
  • Long distance operation.
  • High sensitivity.
  • Multiplexed or distributed measurements – which are used to offset their major disadvantages of high cost and end-user unfamiliarity.
Applications
Fiber optic sensor has a variety of applications that can be found in equipment from computers to motion detectors. Several applications are specifically shown as following:

  • Mechanical Measurement – such as rotation,acceleration, electric and magnetic field measurement, temperature, pressure, acoustics,vibration, linear and angular position, strain, humidity, viscosity etc.
  • Electrical & Magnetic Measurements
  • Chemical & Biological Sensing
  • Monitoring the physical health of structures in real time.
  • Buildings and Bridges – concrete monitoring during setting, crack monitoring, spatial displacement measurement, neutral axis evolution, long-term deformation monitoring, concrete-steel interaction and post-seismic damage evaluation.
  • Tunnels – multipoint optical extensometers, convergence monitoring, shotcrete vaults evaluation, and joints monitoring damage detection.
  • Dams – foundation monitoring, joint expansion monitoring, spatial displacement measurement, leakage monitoring, and distributed temperature monitoring.
  • Heritage structures – displacement monitoring, crack opening analysis, post-seismic damage evaluation, restoration monitoring, and old-new interaction.
  • Detection of Leakage

By this blog, we have learnt some basic knowledge about fiber optic sensor by its classification, characteristics and applications. However, it is not just enough, more knowledge is waiting for us to learn. For more detailed information about fiber optic sensor, welcome to visit Fiberstore or contact us over sales@fiberstore.com.

Polarization Dependent Isolator VS. Polarization Independent Isolator

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Connectors and other types of optical devices on the output of the transmitter may cause reflection, absorption, or scattering of the optical signal. These effects on the light beam may cause light energy to be reflected back at the source and interfere with source operation. In order to reduce the effects of the interference, an optical isolator is usually used. Optical isolator allows a beam of light to stream through a single one way direction. At the same time, it prevents the light from going back in the opposite direction. According to the polarization characteristics, optical isolators can be divided into two types, including polarization dependent isolator and polarization independent isolator. The polarizer-based module makes a polarization dependent isolator, and the birefringent crystal-based structure makes a polarization independent isolator. You may be very confused about them as you find that there is only a little difference via their names. So, what are they and what are the differences between them? This paper will give you the answer.

Polarization Dependent Isolator

The polarization dependent isolator consists of three parts, an input polarizer , a Faraday rotator, and an output polarizer. Light traveling in the forward direction becomes polarized vertically by the input polarizer. The Faraday rotator will rotate the polarization by 45°. The analyser then enables the light to be transmitted through the isolator. Light traveling in the backward direction becomes polarized at 45° by the analyser. The Faraday rotator will again rotate the polarization by 45°. This means the light is polarized horizontally. Since the polarizer is vertically aligned, the light will be extinguished.

principle of polarization dependent isolator

The picture shows us a Faraday rotator with an input polarizer, and an output analyser. For a polarization dependent isolator, the angle between the polarizer and the analyser, is set to 45°. The Faraday rotator is chosen to give a 45° rotation. Because the polarization of the source is typically maintained by the system, polarization dependent isolator is widely used in free space optical systems.

Polarization Independent Isolator

The polarization independent isolator also consists of three parts, an input birefringent wedge, a Faraday rotator, and an output birefringent wedge. Light traveling in the forward direction is split by the input birefringent wedge into its vertical (0°) and horizontal (90°) components, called the ordinary ray (o-ray) and the extraordinary ray (e-ray) respectively. The Faraday rotator rotates both the o-ray and e-ray by 45°. This means the o-ray is now at 45°, and the e-ray is at −45°. The output birefringent wedge then recombines the two components.

principle of polarization independent isolator

Light traveling in the backward direction is separated into the o-ray at 45, and the e-ray at −45° by the birefringent wedge. The Faraday Rotator again rotates both the rays by 45°. Now the o-ray is at 90°, and the e-ray is at 0°. Instead of being focused by the second birefringent wedge, the rays diverge. The picture shows the propagation of light through a polarization independent isolator. While polarization dependent isolator allows only the light polarized in a specific direction, polarization independent isolator transmit all polarized light. So it is usually widely used in optical fiber amplifier.

Comparison of Polarization Dependent Isolator and Polarization Independent Isolator

In fact, you have already understood these two types of isolators according to the contents above. We can see their similarities and differences through the comparison of their definition, working principle and applications. Both of them consist of three parts and have a same principle based on Faraday effect. However, to overcome the limitation of polarization dependent isolator, polarization independent isolator has been developed. Regardless of the polarization state of the input beam, the beam will propagate through the isolator to the output fiber and the reflected beam will be isolated from the optical source. If the extinction ratio is important, a polarization dependent isolator should be used with either polarization maintaining fibers or even regular single-mode fibers. If the system has no polarization dependence, a polarization independent isolator will be the obvious choice.