Fiber Optic Connector Types
Commonly used fiber optic connector types include SC, FC, LC, ST, MU, E2000, MTRJ, SMA , DIN as well as MTP & MPO etc. They are widely used in the termination of fiber optic cables, such as fiber optic pigtail, fiber optic patch cables and so on.

	LC Connector (Lucent Connector) — Ferrule diameter = 1.25mm. LC connectors are licensed by Lucent and incorporate a push-and-latch design providing pull-proof stability in system rack mounts. LC connectors are available in single mode and multimode. Externally LC connectors resemble a standard RJ45 telephone jack. Internally they resemble a miniature version of the SC connector. This type of connectors are commonly used in connecting SFP Transceiver Module in Router/Switch. For example, the optic interfaces of Cisco’s SFP transceivers are all LC connectors.
	SC Connector (Subscriber Connector) — Ferrule diameter = 2.5mm. The SC connector is becoming increasingly popular in single-mode fiber optic telecom and analog CATV, field deployed links. But the most commonly used field is to connect GBIC (100Base-FX) in router/switch. The high-precision, ceramic ferrule construction is optimal for aligning single-mode optical fibers. The connectors’ outer square profile combined with its push-pull coupling mechanism, allow for greater connector packaging density in instruments and patch panels. The keyed outer body prevents rotational sensitivity and fiber endface damage. Multimode versions of this connector are also available. The typical insertion loss of the SC connector is around 0.3 dB.
	ST Connector (Straight Tip) — Ferrule diameter = 2.5mm. ST connector’s high-precision, ceramic ferrule allows its use with both multimode and single-mode fibers. The bayonet style, keyed coupling mechanism featuring push and turn locking of the connector, prevents over tightening and damaging of the fiber end. The insertion loss of the ST connector is less than 0.5 dB, with typical values of 0.3 dB being routinely achieved. ST connector is used extensively both in the field and in indoor fiber optic LAN applications, eg. ODF (optical distribution frame). In addition, ST connector is also used to connect GBIC transceiver, usually for 100Base-F.
	FC Connector (Ferrule Connector) — Ferrule diameter = 2.5mm. The FC has become the connector of choice for single-mode fibers and is mainly used in fiber-optic instruments, SM fiber optic components, and in highspeed fiber optic communication links. This high-precision, ceramic ferrule connector is equipped with an anti-rotation key, reducing fiber endface damage and rotational alignment sensitivity of the fiber. The key is also used for repeatable alignment of fibers in the optimal, minimal-loss position. Multimode versions of this connector are also available. The typical insertion loss of the FC connector is around 0.3 dB.
	MU Connector (Miniature Unit) — Ferrule diameter = 1.25mm. MU is a small form factor SC. It has the same push/pull style, but can fit 2 channels in the same Footprint of a single SC. MU was developed by NTT. It is a popular connector type in Japan. Applications include high-speed data communications, voice networks, telecommunications, and dense wavelength division multiplexing (DWDM). MU connectors are also used in multiple optical connections and as a self-retentive mechanism in backplane applications.
	MTRJ Connector (Mechanical Transfer Registered Jack) — Ferrule diameter = 2.45×4.4 mm. MT-RJ is a duplex connector with both fibers in a single polymer ferrule. It uses pins for alignment and has male and female versions. Multimode only, field terminated only by prepolished/splice method.
	E2000 Connector — Ferrule diameter = 2.5mm. E2000 connector is a plastic push-pull connector developed by Diamond. The E2000 was developed as an improvement on the SC connector design by having: a latch that retains the connector, a dust cap always in place, and a smaller size. The built in dust cap always stays on the connector protecting the ferrule and blocking harmful laser light when the connector is disconnected. E2000 is available for Singlemode and Multimode applications.
	SMA Connector (Sub Miniature A) — Ferrule diameter = 3.14mm. Due to its stainless steel structure and lowprecision threaded fiber locking mechanism, this connector is used mainly in applications requiring the coupling of high-power laser beams into large-core multimode fibers. Typical applications include laser beam delivery systems in medical, bio-medical, and industrial applications. The typical insertion loss of an SMA connector is greater than 1 dB.
	DIN Connector — Ferrule diameter = 2.5mm. DIN connector is a metal screw on connector which is developed by Siemens. Deutsch Telecom mainly uses it. This is a good connector to use where the ruggedness of a metal screw on connector is required but where there is not enough space for a FC Connector.
	MTP and MPO Connector — MTP and MPO are compatible ribbon fiber connectors based on MT ferrule which allow quick and reliable connections for up to 12 fibers. They are intended for installations that require many fiber connections. Up to 12 fibers in a ribbon are stripped to 125um cladding and inserted into 250um spaced parallel grooves. The ferrule also includes two 0.7mm diameter holes, running parallel to the fibers on the outer side of the ferrule. These two holes hold precision metal guide pins which align the fibers with tight tolerances. MTP and MPO connectors feature male and female connector design. Male connectors have two guide pins and female connectors do not. Both connector types need an adapter to mate a pair of male and female connectors. Because MTP and MPO connectors are trying to align so many fibers at once, their coupling loss are typically bigger than single fiber connectors.

History of Different Connector Types
The ST connector is the oldest design of the connectors still in common use. It was the first connector to use a 2.5mm ferrule. The FC and DIN connectors improved on the ST connector by: isolating cable tension from the ferrule, keying the location of the ferrule for angle polishing, and threading onto the adapter for a more positive connection. The SC connector was then developed to eliminate having to screw and unscrew the connector every time and to reduce the cost by molding instead of machining the connector. A big advantage of this push/pull connector over a FC connector is that less room is required between connectors on patch panels. The E-2000 was developed as an improvement on the SC connector design by having: a latch that retains the connector, a dust cap always in place, and a smaller size. As patch panel densities increased the LC and MU connectors were developed to reduce the space required for connectors on patch panels. Both of these connectors use a 1.25mm ferrule. The MT-RJ connector was then developed to put transmit and receive fibers into one connector. This was the first connector to use the MT ferrule design as opposed to a 2.5mm or 1.25mm diameter ferrule. The MTP connector was then developed to increase fiber density even more. The MTP currently has 12 fibers in its MT ferrule however a 24-fiber version is under development.

There are many more influences that lead to the development of these different commonly used connector types. This is why all of the different connector types exist. In fact, there are not only these connector types. A multitude of specialty connectors are launched to the market for different application.

Connector Endface Preparation
Once the optical fiber is terminated with a particular connector, the connector endface preparation will determine what the connector return loss, also known as back reflection, will be. The back reflection is the ratio between the light propagating through the connector in the forward direction and the light reflected back into the light source by the connector surface. Minimizing back reflection is of great importance in high-speed and analog fiber optic links, utilizing narrow line width sources such as DFB lasers, which are prone to mode hopping and fluctuations in their output.

Flat Polish — a flat polish of the connector surface will result in a back reflection of about -16 dB (4%).
PC Polish — the Physical Contact (PC) polish results in a slightly curved connector surface, forcing the fiber ends of mating connector pairs into physical contact with each other. This eliminates the fiber-to-air interface, there by resulting in back reflections of -30 to -40 dB. The PC polish is the most popular connector endface preparation, used in most applications.
UPC/SPC Polish — in the Super PC (SPC) and Ultra PC (UPC) polish, an extended polishing cycle enhances the surface quality of the connector, resulting in back reflections of -40 to -55 dB and < -55dB, respectively. These polish types are used in high-speed, digital fiber optic transmission systems.
APC Polish — the Angled PC (APC) polish, adds an 8 degree angle to the connector endface. Back reflections of <-60 dB can routinely be accomplished with this polish.

Optical isolator variety, including on-line optical isolator, free-space optical isolators, etc. We provide a variety of optical isolators, used to meet the needs of different applications. 1310/1480 / 1550nm polarization-independent optical isolator interior design of two single-mode fiber for craft orthogonal polarization states were treated to ensure the entire device is independent of the polarization characteristics. Unipolar devices with low insertion loss, two-stage device has a high optical isolation, suitable for different applications, mainly used in optical fiber amplifiers, fiber lasers, fiber CATV networks, and satellite communications.

Faraday magnetic media within 1μm ~ 2μm wavelength range usually low optical loss yttrium iron garnet (YIG) single crystal. Novel pigtail input and output optical isolators have a fairly good performance, the minimum insertion loss of about 0.5dB, isolation of 35 ~ 60dB, up to 70dB. Usually the wavelength of the optical isolator to distinguish, 800-1300nm more, there are some specific wavelength.

An optical isolator is a passive optical components allows only unidirectional light through its working principle is based on Faraday rotation of non-reciprocity. Echo reflected light through the fiber can be well isolated optical isolators. The main advantage of optical isolator Faraday effect of magneto-optic crystal. Optical isolator features are: positive low insertion loss, high reverse isolation, high return loss. An optical isolator is blocked to allow the light to one direction and the opposite direction by the passive components, the role of limiting the direction of light, the light transmission in one direction only, the reflected return light passes through the optical fiber can be an optical isolator good isolation to improve the transmission efficiency of light.

OF-Link Communications Co., Ltd is a manufacturer and exporter specialized in fiber optic passive components. We focus on offering products with premium quality and competitive prices in the field of optical fiber communications, fiber laser and fiber sensor applications.

principle is based on Faraday rotation of non-reciprocity. Echo reflected light through the fiber can be well isolated optical isolator. The main advantage of the optical isolator   magneto-optical Faraday effect transistor. Optical isolator features are: positive low insertion loss, high reverse isolation, high return loss. The optical isolator allows the light to one direction is prevented by the opposite direction by the passive components, the function is to limit the direction of the light, the light transmission in one direction only, the reflected return light passes through the fiber optical isolator can be good isolation and improve light transmission efficiency, optical isolator is characterized by high isolation, low insertion loss; high reliability, high stability; very low polarization dependent loss and polarization mode dispersion. Its role is to prevent the adverse effects of light and transmitted light generated by the optical system, e.g., between the semiconductor laser source and an optical transmission system is installed in the optical path due to various causes an optical isolator can largely reduce the adverse effects of reflected light on the stability of the light source spectral output power generated. In the high-speed direct modulation direct detection optical fiber communication systems, the transmission of the light will produce additional noise in the system performance degradation, which also requires an optical isolator to eliminate. Both ends of the fiber amplifier doped fiber isolator is mounted glazing can improve the stability of the optical fiber amplifier, without it, the reflected light enters the source (laser), causing severe fluctuation source. In coherent optical long-distance optical fiber communication systems, at some distance install an optical isolator can reduce the power loss caused by stimulated Brillouin scattering by. Thus, the optical isolator has an important role in optical fiber communication, optical information processing systems, and precision measuring optical fiber sensing system.

The main advantage of the Fiber optical isolator magneto-optical Faraday effect transistor. Faraday Faraday effect was first observed in 1845 is not optically active material in the magnetic field by rotating the polarization direction of light occurring substance, also known as magneto-optical effects. Polarized light transmitted along the magnetic field, whose direction of polarization rotation angle θ and the magnetic field strength B and the material is proportional to the length L of the product. Optical isolator works shown in Figure 1. For normal incident signal light, through a polarizer becomes the linearly polarized light, the Faraday rotating magnetic medium and the polarization direction of the external magnetic field with the right hand 45 of the signal light, and just make a low loss through the polarizer 45 placement of the analyzer. For the reverse light, a polarization analyzer after the placement of the media line deflection direction is right-rotated by 45 degrees, thereby reversing the direction of polarization of the light and the direction perpendicular to the polarizer, the reflected light is completely blocked transmission . Faraday magnetic media within 1μm ~ 2μm wavelength range usually low optical loss yttrium iron garnet (YIG) single crystal. New pigtail input and output optical isolator has a very good performance, the minimum insertion loss of about 0.5dB, isolation of 35 ~ 60dB, up to 70dB.

OF-Link Communications Co., Ltd. is a manufacturer and exporter specializing in optical passive components. We focus on providing high quality products with competitive quality and price of applications in optical fiber communication, fiber lasers and fiber-optic sensor. Main products have polarization maintaining (PM) fiber optic components, high power fiber laser components, high power fiber laser components, high power fiber laser components, high power fiber laser components, fused / filter fiber coupler, WDM, CWDM, DWDM, bandpass filter, fiber optical isolators and circulators, variable optical attenuator (VOA), fiber collimator, fiber distribution cables and so on. OF-LINK is located in Shenzhen, China, fiber optic components based on their business nine years of experience in; our production facilities have passed the ISO 9001:2008 certification, providing products comply with RoHS, IEC and Telcordia requirements. Our 100% visual and optical testing to ensure that all products meet international industry standards.

With optical manufacturing capabilities, testing services, global logistics and supply chain management, OF-LINK is ready to meet the special requirements of customers from around the world the full spectrum. Our customers are mainly manufacturers at the University of telecommunications, fiber lasers and fiber-optic sensors, and research institutes around the world. Due to the high demand for fiber optic networks and the development of a larger fiber optic products, in 2009, OF-LINK merged with Compass Technology Co., Ltd. is located in Jiangsu Nantong City Chongchuan Development Zone, Jiangsu Province. This is a high-tech company who is engaged in the application of Beidou satellite and fiber-optic communications; OF-LINK participate in its optical parts, and solely responsible for the overseas market. We completed the production of one million units in line timing device 900 million units, “fiber optic connectors and 100 million units,” the PLC splitter annual building. The project was included in the major scientific and technological achievements into special funds for the project, and has broad prospects for the industry. OF-LINK idea is first to meet customer needs: quality and reliability assurance, timely delivery and reliability, to protect customers’ intellectual property (IP), efficient supply chain management, comprehensive and timely customer response system that allows its better serve the majority of consumers. Our company offers fiber optic isolators, quality assurance, affordable, hope there is a demand can come to purchase.

If it came down to a contest between on-page optimization efforts against link building efforts, links would win hands down. You may find it shocking to hear a President of an optimization firm saying such a thing, but its true. I would challenge anyone to outrank a website that has a massive number of quality back links by using on-page optimization efforts alone with zero link building efforts. Whereas, you can easily outrank a website that is extremely well optimized by focusing heavily on link building efforts. An interesting example is Apple.com. One of the most important elements of optimization is to place the target key phrase within the meta title tag. However, search for the word “computers” on Google and you will find Apple.com on the first page of results. Apple does not even mention the word computers in their meta title tag. How is this possible when there are literally millions of competing websites that are aggressively trying to show up for this term by applying various optimization efforts? The answer is that Apple.com has a superior volume of back links (over 70,000 in Google alone). And a large percentage of these links include the word computers within the anchor text (i.e. Apple Computers, Mac Computers, etc.).

Does this mean Optimization is dead?

The answer of course, is no. Search engines still love websites that have tons of fresh and relevant content. It is the basis of what search engine results are all about. Copywriting fees are worth every penny when it comes to adding well written descriptions of your products and services onto your website. Professional optimization companies still flourish because of the success they bring to their clients through increased rankings and traffic. For optimum results, you need both optimization and links to succeed today.

It’s not just the quantity of incoming links, but the quality and relevance of the websites from which they come, as well as what words are used within the visible text portion of the hyperlinks, i.e. “anchor text.” Reciprocated links have less value than they use to and can potentially hurt your rankings if you are exchanging with too many unrelated websites, i.e. bad neighborhoods. One-way links are the best links.

During the last few Search Engine Strategies conferences, I could not help but notice an increasing number of link-related workshops, including a class dedicated to purchasing text links. Matt Cutts, official spokesman and software engineer for Google shared how he personally believes that buying links is like a politician buying votes and that incoming links should only grow naturally. He shared that the best way to receive incoming text links was to offer something truly helpful and/or unique and interesting to the public and that this would generate free unsolicited, incoming links without even asking. He offered some extreme examples of very creative websites, which caused a national media stir. Within minutes frustrated attendees spoke up about how the search engines started this whole thing by giving too much criteria to links in the first place, and that buying links on other sites (be it through banners or text links) has been a conventional form of advertising well before Google even existed.

Some commented that if Google was considering penalization for sites that buy or sell links, they should start with Yahoo, since Yahoo earns a good portion of their income from selling paid text links (i.e. $299/year directory listings). Interesting enough, Google actually recommends on their website that you submit to directories such as Yahoo.

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An exclusive touch is necessary to splice fiber optic cable since the glass fibers are encased with fiber insulation sealed in the plastic coating. Unlike copper, the fibers are delicate and is easily broken by using excessive pressure to chop the casing while splicing cables to fiber connectors.

The splicing process begins by preparing each fiber end for fusion. Fusion splicing necessitates that all protective coatings be removed from the ends of each and every fiber. The fiber will then be cleaved using the score-and-break method. Each fiber face to achieve an excellent optical finish by cleaving and polishing the fiber end. Prior to the connection is made, get rid of each fiber have to have an effortless finish that’s clear of defects including hackles, lips, and fractures. These defects, along with other impurities and dirt customize the geometrical propagation patterns of light and cause scattering. The quality of each fiber end is inspected using a microscope. In fusion splicing, splice loss is a direct purpose of the angles and excellence of the two fiber-end faces.

The fusion splicing is just one of a splice cables method. The fundamental fusion-splicing apparatus includes two fixtures which the fibers are mounted with two electrodes. An inspection microscope aids in the position with the prepared fiber ends in a fusion-splicing apparatus. The fibers are placed in the apparatus, aligned, and then fused together. Initially, fiber optic fusion splicer used nichrome wire as the atomizer to melt or fuse fibers together. The heater is undoubtedly an electric arc that softens two butted fiber ends and permits the fibers to become fused together.

In Mechanical Splicing, mechanical splices are only alignment devices, built to hold the two fiber ends in a precisely aligned position thus enabling light to pass through from fiber in the other. Mechanical splicing is done in an optical junction the location where the fibers are precisely aligned and located in place by the self-contained assembly, not only a permanent bond. This technique aligns both fiber ends to some common centerline, aligning their cores and so the light can pass from one fiber to an alternative. This is accomplished using a portable workstation that is utilized to get ready each fiber end. That preparation includes stripping a skinny layer of plastic coating from your fiber core before its splicing.

Connecting two fiber-optic cables requires precise alignment from the mated fiber cores or spots within a single-mode fiber-optic cable. This can be required in order that the majority of the light is coupled in one fiber-optic cable across a junction to another fiber-optic cable. Actual contact relating to the fiber-optic cables is not even mandatory.

Splices could also be used as optical attenuators if you have a need to attenuate a high-powered signal. Splice losses all the way to 10.0 dB can be programmed and inserted in to the cable if desired. By doing this, the splice can become an in-line attenuator with all the characteristic non reflectance of the fusion splice. Typical fusion-splice losses can be estimated at 0.02 dB for loss-budget calculation purposes. Mechanical splices are typically implemented in the field, require little if any tooling, and give losses of around 0.5 to 0.75 dB.

FiberStore provides a comprehensive range of hand tools, network tool kits and consumables for the installation and maintenance of LAN, fibre optic and copper networks. Whether you require a punchdown tool, RJ45 / Cat 5 Crimping tool, fiber splicer or automatic wire stripper or a complete network tool kit, FiberStore has the right tools for your needs. We provide fully automatic fibre optic fusion splicers from Fujikura for multimode and singlemode optical fibre cables, ensuring the best fibre termination possible whether an expert or a novice..
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To understand just how vital a part vibration isolators play in today’s technological advances one need only scour the articles that go along with the high-tech industry’s latest headlines. In the past month alone, an examination of no less than three such articles revealed references to them. And these mentions weren’t just passing asides either. In all cases, the vibration isolators proved instrumental in putting the technologies being discussed in the spotlight.

The first up among these recent news reports involved a high speed multi-axis optical micrometer. As Automation World pointed out, this device not only “sets a new standard for high speed and high precision diameter inspection” but also “eliminates errors that were previously endemic to optical micrometers.” And yep, you guessed it, there are vibration isolators behind all those capabilities. The publication went on to praise the micrometer for possessing no moving parts, which dramatically increases its durability. Delving deeper into the specifics, Automation World stresses, “Incorporating a custom designed vibration isolation system within the head, the [micrometer] is able to resist damage from vibration and impact.”

Up next was a review of the 2014 Honda Acura MDX, whose advanced engineering has driven the SUV to the top of its vehicle class. Pointing to the sport utility vehicle’s ability to give consumers the fuel efficiency and affordability they crave without sacrificing “panache and human comfort accouterments,” the Honda Acura was recognized by Kiplinger’s Report and U.S. News and World report as both “2014 Best Value in a full-size luxury SUV” and “Best car for the money.”

So how do vibration isolators play into all of this, you ask. The reviewers closed their praise of the SUV with this praise: “We especially appreciate superior body roll stability and road vibration isolation via electronic sway control, fluid filled body mounts and exceptional sound deadening materials installed beneath seamless carpeting and in the rear wheel wells.”

Third but not least among the news nods came from TVTechnology.com. The tech website specifically looked at portable storage, marveling over its uncanny ability to increase in power and capability despite shrinking in size. One of the storage devices it lauded is the Sonnet Fusion F3 for “managing high-speed storage when in the field.” This portable storage device facilitates high-speed storage when on location and has a case that “is designed to withstand rough handling. Moreover, “each of the F3 drives is mounted on its own multi-axis shock vibration isolation sled to try and eliminate vibration problems.”
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Light waves consist of oscillating electric and magnetic fields. These two fields are perpendicular to each other and to the direction of light traveling. We call the electric field plane as the light’s polarization.

Sunlight and many other ordinary light is made of many light waves, each with their electric and magnetic fields oriented randomly. If all waves’ electric fields were aligned parallel to each other, we call this light linearly polarized.

* Polarization’s effect on optical fibers

Polarization does not really matter in multimode fibers but it can be crucial in single mode fibers especially for long distance and high speed rate fiber communications. Why? Let me explain it below.

Technically speaking, single mode fibers actually have two modes traveling in it. These two modes have orthogonal polarization and perfect single mode fibers cannot differentiate between them. These two modes are functionally identical and light energy can shift easily between these two polarization modes.

However, fiber’s geometry is not perfect. As a result, these two modes actually travel along the fiber at slightly different speeds. The effect is called PMD (polarization mode dispersion). The slight speed difference can cause problems in high speed fiber optic links such as 10Gbit/s and 40Gbit/s.

* Polarization maintaining fibers come to the rescue!

Polarization maintaining fibers are special kinds of single mode fibers, they are also commonly called PM fibers or Panda PM fibers.

PM fibers have built-in asymmetry which is also called birefringence. The refractive index of PM fiber differs for the two polarizations and this effect prevent light energy from coupling between two polarizations.

PM fibers can transmit light in a single polarization if the input light polarization is aligned to one of its two birefringence axes. And that is why they are called polarization maintaining fibers.

* The applications of polarization maintaining fibers

PM fibers are rarely used for long distance transmission because of their expensive price and higher attenuation than single mode fiber. They are commonly used for telecommunication applications, fiber optic sensing and interferometry.

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Light waves consist of oscillating electric and magnetic fields. These two fields are perpendicular to each other and to the direction of light traveling. We call the electric field plane as the light’s polarization.

Sunlight and many other ordinary light is made of many light waves, each with their electric and magnetic fields oriented randomly. If all waves’ electric fields were aligned parallel to each other, we call this light linearly polarized.

* Polarization’s effect on optical fibers

Polarization does not really matter in multimode fibers but it can be crucial in single mode fibers especially for long distance and high speed rate fiber communications. Why? Let me explain it below.

Technically speaking, single mode fibers actually have two modes traveling in it. These two modes have orthogonal polarization and perfect single mode fibers cannot differentiate between them. These two modes are functionally identical and light energy can shift easily between these two polarization modes.

However, fiber’s geometry is not perfect. As a result, these two modes actually travel along the fiber at slightly different speeds. The effect is called PMD (polarization mode dispersion). The slight speed difference can cause problems in high speed fiber optic links such as 10Gbit/s and 40Gbit/s.

* Polarization maintaining fibers come to the rescue!

Polarization maintaining fibers are special kinds of single mode fibers, they are also commonly called PM fibers or Panda PM fibers.

PM fibers have built-in asymmetry which is also called birefringence. The refractive index of PM fiber differs for the two polarizations and this effect prevent light energy from coupling between two polarizations.

PM fibers can transmit light in a single polarization if the input light polarization is aligned to one of its two birefringence axes. And that is why they are called polarization maintaining fibers.

* The applications of polarization maintaining fibers

PM fibers are rarely used for long distance transmission because of their expensive price and higher attenuation than single mode fiber. They are commonly used for telecommunication applications, fiber optic sensing and interferometry.

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The typical construction of an circulator consists of a number of walk-off polarizers, half-wave plates and Faraday rotators. Typically an optical ciruclator has three or four ports.

A variety of circulators are available commercially. They have low insertion loss, high isolation over a wide wavelength range, minimal polarization dependent loss, and low polarization mode dispersion.

The typical insertion loss of an isolator is about 0.6dB, channel isolation is over 40dB, optical return loss is over 50dB and polarization dependent loss is lower than 0.1dB.

The applications of optical ciruclators

In advanced optical communication systems, circulators are used for bi-directional transmissions, WDM networks, fiber amplifier systems, and for optical time domain reflectometer (OTDR) measurements.

Optical circulators are essential compoents of optical communication systems. They enable the routing of light from one optical fiber or waveguide to another based upon the direction of light propagation.

More information

Optical ciruculators extend the basic idea behind an optical isolator and add more functionality to the device. A circulator does not disgard the backward propagating light, as an isolator does, but directs it to another port, thus resulting in a three-port device in the simplest configuration. More ports can be added if one wants to redirect light coming from the third port to a fourth port. Even six ports circulators exist which direct light to different ports in a circular fashion depending on which port light enters.

You may guess that with the increasing of ports, the design becomes increasingly complex. You are absolutely correct on that guess. A second layer of complexity is added for polarization-independent circulators because they must split the incoming light from any port into its orthogonally polarized components and process each component separately.

In general, a circulator requires a large number of parts. The most important component in a polarization independent circulator is the beam displacer. Beam displacer is made from a strongly birefringent medium such that it displaces the orthogonally polarized components spatially by different amounts.

In spite of their complexity, optical circulators are available commercially in a relatively compact size with fiber pigtails on each end. Insertion losses are also very acceptable for such complex devices.

Optical circulators have found many applications in designing lightwave systems. A example could be a three-port circulator used with a fiber grating to realize a narrowband bandpass filter working in transmission. The circulator coverts the device into a transmission filter for all practical purposes..
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