分类目录归档:PON Systems

Comparison Between EPON and GPON

PON is the abbreviation of passive optical network, which only uses fiber and passive components like splitters and combiners. EPON (Ethernet PON) and GPON (Gigabit PON) are the most important versions of passive optical networks, widely used for Internet access, voice over Internet protocol (VoIP), and digital TV delivery in metropolitan areas. Today we are going to talk about the differences between them.

PON network

Technology Comparison

EPON is based on the Ethernet standard 802.3 that can support the speed of 1.25 Gbit/s in both the downstream and upstream directions. It is well-known as the solution for the “first mile” optical access network. While GPON, based on Gigabit technology, is designated as ITU-T G.983 which can provide for 622 Mbit/s downstream and 155 Mbit/s upstream. GPON is an important approach to enable full service access network. Its requirements were set force by the Full Service Access Network (FASN) group, which was later adopted by ITU-T as the G.984.x standards–an addition to ITU-T recommendation, G.983, which details broadband PON (BPON).

As the parts of PON, they have something in common. For example, they both can be accepted as international standards, cover the same network topology methods and FTTx applications, and use WDM (wavelength-division multiplexing) with the same optical frequencies as each other with a third party wavelength; and provide triple-play, Internet Protocol TV (IPTV) and cable TV (CATV) video services.

Costs Comparison

No matter in a GPON or in an EPON, the optical line terminal (OLT), optical network unit (ONU) and optical distribution network (ODN) are the indispensable parts, which are the decisive factor of the costs of GPON and EPON deployments.

The cost of OLT and ONT is influenced by the ASIC (application specific integrated circuit) and optic module. Recently, the chipsets of GPON are mostly based on FPGA (field-programmable gate array), which is more expensive than the EPON MAC layer ASIC. On the other hand, the optic module’s price of GPON is also higher than EPON’s. When GPON reaches deployment stage, the estimated cost of a GPON OLT is 1.5 to 2 times higher than an EPON OLT, and the estimated cost of a GPON ONT will be 1.2 to 1.5 times higher than an EPON ONT.

We all know that the ODN is made up of fiber cable, cabinet, optical splitter, connector, and etc. In the case of transmitting signals to the same number of users, the cost of EPON and GPON would be the same.

Summary

Nowadays, since many experts have different opinions on GPON and EPON. Thus, there is no absolute answer to determine which is better. But one thing is clear: PON, which possesses the low cost of passive components, has made great strides driven by the growing demand for faster Internet service and more video. Also, fiber deployments will continue expanding at the expense of copper, as consumer demands for “triple-play” (video, voice and data) grow.

FTTH: Bringing You the Life-enhancing Benefits

FTTH, which is short for fiber to the home, is an ideal fiber optic architecture as the fiber optic service to home. It can transport large amount of data from caller to caller fast and reliable. In the light of present situation, there are more than 10 million homes all over the world adopted FTTH network in that it holds many advantages over current technologies. Here let us figure them out.

FTTH_architecture

Benefits of FTTH

Some experts has pointed that fiber-to-the-home connections are the only technology with enough bandwidth to handle projected consumer demands during the next decade reliably and cost effectively. Of course, we all know that FTTH is a passive network that do not need active components. This feature makes it dramatically minimize the network maintenance cost and requirements. What is more, it features local battery backup and low-power consumption, which indeed bring much convenience to people’s lives. But, are that all its advantages? I am afraid that these simple advantages can’t convince people that FTTH can bring the life-enhancing benefits to their lives. And so do you. So, what are its remarkable benefits? Please take a look at the blow words.

The first thing you should know that it is less susceptible to corrosion or power surges from lightning and other sources, resulting in greater reliability. Because of its higher stability and less interruptions, it replaces copper infrastructure with new technology, allowing for future evolution of technology.

Second, it can provide virtually unlimited bandwidth capacity. As we mentioned above, it can support large amounts of data and keep up with consumer and technology demands, which makes it access to more advanced communication products like streaming video, internet TV, quality video conferencing, “smart home” technology, IP video home monitoring, gaming and so on.

Third, it brings profits to your home and the community. According to the Fiber-to-the-Home Council, we have got a amazing data that FTTH has increased the home value as much as $5,000. With the advanced technology, it made the “global village” come true. Even at ultra-rural areas, people still can compete on a global scale in their work or business.

Two Factors You should know before deploying FTTH

Now that we have learned the benefits of FTTH, I guess some people may intend to deploy FTTH network. Fiber deployment is a trade-off driven by the cost of the service relative to the potential revenue per subscriber. So before you deploy it, please read the below tips which can help you avoid loss.

Deploy the fibers in the high economic density of the service area. The number of houses and enterprises that a fiber passes by will be translated into the number of money. So , if you deploy your network in a high economic density place, you will get your investment back and make high profits soon.

Deploy your network in the place where has existed current fiber/copper wiring. It is easiest to serve a given area by following the current conduits and loops and staying with the rough topology of the old installation. This method will save you a lot of money compared with restarting wiring for your network. So if you can’t run the fiber directly to the home, just take it is to the node where the loops currently collect.

Conlusion

Recently, FTTH has been adopted by thousands of families, and the continuous prosperity will last for a long time. If you want to deploy a FTTH network, you can come to Fiberstore to get the needful tools. In Fibersotre, you can find the most cost-effective FTTH solutions including FTTH fiber cables, fiber optic splitters and some others. They are all tested in good condition with reasonable prices. So, if you choose Fiberstore, you just choose your better FTTH network with low cost.

Differences Between FBT Splitter and PLC Splitter

Nowadays, with the further popularization of the optical fiber communication, fiber optic splitter plays an increasing significant role in many of today’s optical network topologies. Although there are variations of splitter types, the two most commonly deployed splitters are FBT (Fused Biconical Taper) splitter and PLC (Planar Lightwave Circuit) splitter. So, when you deploy your network, what kind of splitter you should choose may be a problem for you. And in order to solve this problem, this paper will give you a detailed introduction of differences between FBT splitter and PLC splitter.

Definition of FBT Splitter and PLC Splitter

Before you get to know the features of them, first you should know what them are. Next, each splitter will be introduced.

FBT Splitter – FBT is a traditional technology that two fibers are typically twisted and fused together while the assembly is being elongated and tapered. The fused fibers are protected by a glass substrate and then protected by a stainless steel tube, typically 3mm diameter by 54mm long. FBT splitters are widely accepted and used in passive optical networks, especially for instances where the split configuration is not more than 1×4. The slight drawback of this technology is when larger split configurations such as 1×16, 1×32 and 1×64 are needed.

PLC splitter – A PLC splitter is a micro-optical component based on planar lightwave circuit technology and provides a low cost light distribution solution with small form factor and high reliability. It is manufactured using silica glass waveguide circuits that are aligned with a V-groove fiber array chip that uses ribbon fiber. Once everything is aligned and bonded, it is then packaged inside a miniature housing. PLC Splitter has high quality performance, such as low insertion loss, low PDL (Polarization Dependent Loss), high return loss and excellent uniformity over a wide wavelength range from 1260 nm to 1620 nm and have an operating temperature -40°C to +85°C.

Feature Comparison of FBT Splitter and PLC Splitter

In the past few years, splitter technology has made a huge step forward, especially the PLC splitter technology. This situation resulted in that PLC splitter has become a higher reliable type of device compared to the traditional FBT splitter. Although being similar in size and appearance, the internally technologies behind these types vary, thus giving service providers a possibility to choose a more appropriate solution.

Operating Wavelength – As is mentioned above, PLC splitter can provide a range of operating wavelength from 1260 nm to 1620 nm. But FBT splitters only support three wavelengths (850/1310/1550 nm) which makes these devices unable to operate on other wavelengths.

Operating Temperature – Commonly, FTB splitter is to a high extent temperature sensitive, providing a stable working range of -5 °C to 75 °C. While PLC splitter operates at wider temperature range (-40 °C to 85 °C), allowing its deploying in the areas of extreme climate.

Split Ratio – The split ratio of FBT splitter is 1:8 and it can be higher with higher failure rate. The split ratio of PLC splitter can go up to 64, which is equal to all branches, thus providing a high reliability.

Cost – FBT splitter is made out of materials that are easily available, for example steel, fiber, hot dorm and others. All of these materials are low-price, which determines the low cost of the device itself. PLC splitter manufacturing technology is more complex. It uses semiconductor technology (lithography, etching, developer technology) production, hence it is more difficult to manufacture. Therefore, the price of this device is higher.

FBT and PLC splitter feature comparison

Conclusion

In a word, Compared with FBT splitter, the capacity of PLC splitter is better, but costlier than the FBT splitter in the smaller ratios. You can choose it according to your requirements. Fiberstore offers both FBT splitter and PLC splitter with good quality and low price. Whether in FTTx systems or in traditional optic network, Fiberstore splitter can help you to maximize the functionality of optical network circuits.

Are You Familiar with Fiber Optic Coupler?

Optical coupler is the extremely important component in a number of phonics devices and systems that couple or split light through wave-guides or fibers. Fiber optic couplers can be either active or passive devices. The difference between active and passive couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active couplers are electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output.

fiber optic coupler

A basic fiber optic coupler has N input ports and M output ports (showed in the above picture) which typically range from 1 to 64. But generally, they are four-port devices and their operation relies on the distributed coupling between two individual waveguides in close proximity, which results in a gradual power transfer between modes supported by the two waveguides. The brief principles of four-ports fiber optic coupler is given in the following picture. If light enters into the port 1, it will be splitted into the output ports between ports 3 and 4. And port 2 functions in the same way. And sometimes, one of port 1 or port 2 is unused, so the fiber optic coupler will act as a Y or T coupler (Y or T stands for the form of transmission route).

brief principles of four-ports fiber optic coupler

As we have known before, fiber optic coupler can couple or split light, so it also can be called fiber optic splitter. In fact, splitter is named for the function of the device, coulper named for its working principle. These days, the most popular types are fused fiber optic couplers and planar lightwave circuit (PLC) splitter.

Fused fiber optic coupler is a kind of fiber optic couplers, which is formed based on fused biconical taper (FBT) technology. Therefore, it is also known as FBT coupler. It can work on three different operating bands such as 850nm, 1310 nm and 1550nm.

Planar Lightwave Circuit (PLC) Splitter is designed to manage the power of optical signals through splitting and routing. It can provide reliable light distribution and is based on planar lightwave circuit technology. Compared with FBT fused coupler of lower cost, PLC splitter has wider operating wavelength range which is from 1260 nm to 1620 nm, and wider temperature range from -40ºC to +85ºC, better uniformity, higher reliability and smaller size.

Currently, fiber optic coupler is widely used in that it can support FTTX (FTTP, FTTH, FTTN, FTTC), passive optical networks (PON), local area networks (LAN), CATV systems, amplifying, monitoring system and test equipment. As a result, fiber optic coupler with good quality is required. Fiberstore can offer you various kinds of fiber optic couplers with good quality, including fused fiber optic coupler and Planar Lightwave Circuit (PLC) Splitter. For more information, you can visit Fiberstore.

A Guide for PON

Nowadays, there is a growing popularity of Video-on-Demand (VoD), VoIP and increased IPTV deployment. Providers aim to offering fiber-to-the-home (FTTH), (fiber-to-the-building) FTTB and fiber-to-the-curb (FTTC) solutions through advancing passive optical network (PON) technology. The term “PON” may confuse you for its complexity and extensiveness. Details are as followed.

PON is a single, shared optical fiber that uses inexpensive optical splitters to divide the single fiber into separate strands. It can build up a point-to-point topology supporting 1Gbps transmission to home and business typically within 20km. PON system is called “passive” because that there are no active electronics within the access network. It uses optical splitters to separate and collect signals rather than electrically powered switching equipment.

PON consists of an Optical Line Terminal (OLT) connected to multiple Optical Network Units (ONUs) via an Optical Distribution Network (ODN).

OLT: it is a device at the service provider’s central office, performing conversion between the electrical signals used by the service provider’s equipment and the fiber optic signals used by the passive optical network and coordinating the multiplexing between the conversion devices on the other end of that network.

ODN: it is used for distributing signals to users in a telecommunications network by optical fiber. ODN has been made up entirely of passive optical components particularly singlemode optical fibers and optical splitters.

ONUs: they are devices near end users, delivering traffic-load information provided by OLTs to each end user.

PON System

PON system has achieved significant deployment in today’s FTTx networks especially in FTTH networks as the development of Gigabit passive optical network (GPON) and Ethernet passive optical network (EPON). Nowadays, GPON and EPON are the mostly widely used types of PON for their low cost, high bandwidth, great flexibility and easy management, etc.

GPON: it is defined by ITU-T recommendation series G.984.1 through G.984.6. It can transport not only Ethernet, but also ATM and TDM (PSTN, ISDN, E1 and E3) traffic. It supports services like carrying video and delivering video on single fiber distribution, allowing low-consuming transmission, more efficient maintenance, cabling and overall performance.

EPON: it is defined by the Ethernet standard rather than by the ATM standard, making you utilize the economies-of-scale of Ethernet. It can provide simple and easy-to-manage connectivity to Ethernet-based, IP equipment both at the customer premises and at the central office. It is perfect for voice and video traffic solution as with other Gigabit Ethernet media.

GPON and EPON

 For more information about OLTs, Optical Splitters and ONUs, please visit www.fs.com.

Originally published at: www.fiber-optic-equipment.com/a-guide-for-pon.html

Mobile Internet strategy – Increase broadband

As the use of mobile applications and services that require increasingly more bandwidth continues to grow, wireless service providers must find cost-effective and efficient methods for meeting the bandwidth demand. Legacy transport networks are no longer capable of adequately serving today’s cell sites. Newer technologies such as GPON, WDM-PON, and Ethernet over CWDM/DWDM are all well-suited to cost-effectively address the growing bandwidth needs of wireless service providers. Regardless of the technology used, Fiberstore product is an integral part of the solution.

GPON

While GPON has been adopted as a technology of choice in high-speed access networks for inexpensive residential service delivery, more recently, it has begun to spread into business access.  With the ability to deliver up to 10Gbps per GPON OLT port, it can also be a cost-effective technology for delivering higher bandwidth to cell towers.
GPON

Figure 1: GPON Network

Whether the GPON splitters are collocated with the OLT or distributed in the field, it is likely that a multiple of splitter modules would be needed to handle each serving area.  To aid with this, the SplitLight HD can provide up to 16 GPON splitters in a single, 1RU chassis, while traditional solutions can only provide a single GPON splitter in the same footprint. In addition, legacy LGX solutions would require at least 4RU to deliver the same density.

WDM-PON

Building on the advantages of GPON, shared infrastructure and a single OLT transponder, WDM-PON provides the added advantage of delivering a dedicated wavelength to each GPON ONT. WDM-PON does not use a splitter. Instead, an Arrayed Waveguide Grating (AWG) is used to multiplex and de-multiplex wavelengths between the feeder fibers and distribution fibers. The result is dedicated bandwidth and a more secure network for each subscriber, or in this case, cell tower. Another advantage of WDM-PON is the ability to add/drop wavelengths at intermediate cell towers that lie between mobile switching centers.
WDM-PON

Figure 2: WDM-PON Network
As with GPON splitters, it is likely that multiple AWGs would be required at both ends of the WDM-PON network. The SplitLight HD can also house up to 12 AWGs in a single, 1RU chassis. In addition, the SplitLight HD has the flexibility to also house passive OADMs for the intermediate add/drops.

There are four key points of 10G EPON technology

With the major carriers “Broadband speed”, “Light of Copper” project extensively, The future will be a multimedia broadband services, video on demand, interactive games as the main feature, high-bandwidth, integrated operators will be judged promoted by the merits of the standard broadband products.

Under the broadband Fiber Optic Network in the trend, PON technology has become the world’s attention to various telecom operators hot technology is one of the operators to implement “broadband speed”, “Light of Copper” engineering technology base. Wheter EPON, or GPON, which provides only for the uplink and downlink bandwidth of

1. Defines six 10G EPON optical power budget, in view of the asymmetric mode PRX10, PRX20 and PRX30 as well as for symmetric mode PR10, PR20 and PR30, these six kinds of optical power budget model is basically to meet the construction needs of the service provider network;

2. 10G EPON technology in achieving the 1G EPON conventional multi-point control protocol layer (MPCP) based on the forward compatibility, also extended the original message type, for reporting optical terminal equipment, EPON OLT/EPON ONU Fiber Transceiver switch time to meet the 10G EPON network requirements;

3. 10G EPON uses (255, 223) Forward Error Correction (FEC) encoding method, the encoded with FEC coding for the same strain of 1G EPON, but its strong support 10G EPON coding gain can lower the sensitivity of the optical receiver;

4. 10G EPON uplink and downlink wavelength for the re-planning, downlink using 1268-1280nm wavelength, then reuse the original uplink of 1G EPON 1575-1580 nm wavelength, the wavelength in order to avoid conflicts, 10G EPON uplink only use time division multiple access (TDMA) manner.

Has been released G.987.1 standard that defines 10G GPON system’s overall technical requirements and system architecture, clearly put forward the 10G GPON system to ensure good QoS, based on the traditional telecom services to fully support all emerging businesses and the same time, also provides dynamic Bandwidth Allocation (DBA) algorithm, energy saving, authentication and encryption related content to inherit the original 1G GPON suppliers; The G.987.2 is the focus of standardized 10G GPON physical layer parameters, including downlink rate, ODN power budget, splitting ratio, up and down the line wavelength range and line coding, etc., although down the line of 10G EPON same wavelength range and 10G EPON, GPON but due to the wavelength with 1G is not conflict, therefore, 10G GPON uplink and downlink are used wavelength division multiple access (WDMA) manner.

A complete industrial chain, including chip PON, optical modules and equipment three links. If to analysis PON industry chain, it need to start from the three links, analysis of every link current development status and future development trend.

Overall, 10G EPON and 10G GPON is currently not reach the requirements of large-scale commercial applications, although some equipment manufacturers have recently introduced a 10G EPON or 10G GPON products, and with operators, the creation of some experimental inning, but still in the laboratory testing phase, is still some distance away from the large-scale commercial.
10G PON technology to meet future access networks, “large-capacity, fewer offices,” the direction of development, while improving access speed, supports larger branching ratio, covering more users. Therefore, 10G PON technology will become the future telecom operators to achieve “broadband speed”, “Light of Copper” and other broadband network construction hot technology for sustainable development.

Fiberstore’s PON Splitter Modules-Your Best Alternative for FHHx Solution

FTTx is short for the Fibre-to-the-X, where X can denote a number of destinations. These include Home (FTTH), Premise (FTTP), Curb (FTTC), Building (FTTB), User (FTTU) and Node (FTTN). Clearly, however, there are overlaps in meaning. FTTP is similar to FTTB, and FTTC resembles FTTN.

As consumers world over have been demanding more and more bandwidth hungry applications at the network, networks of the future will be digital and intelligent and will offer high transmission capacity and flexible bandwidth. In addition to being easily accessible while offering services that are personalized and tailored to individual need. To support it, FTTx technology, as a effectively one, is widely used in our life nowadays.

Passive Optical Network (PON), a new technology for networking infrastructure, is widely deployed in today’s FTTx network in new installations and is generally considered suitable for consumer broadband services.
As an indispensable component of Passive Optical Network (PON) systems, PON splitter is used to distribute or combine optical signals, installing in an outside plant enclosure and giving carriers the ability to split optical signals to multiple homes or businesses.

1xN Splitter working in the HFFx

According to the Fiber Optic Splitter principle, there are two kinds of PON splitter: EPON OLT/EPON ONU/GPON ONT/GPON OLT. Between them, PLC splitter is valued by its wider operating wavelength because PLC splitter can work on 1260-1650nm wavelength, while FBT can usually work on three different operating wavelengths. What’s more, depending on its split configuration, there are types of PLC splitter designed in 1xN and 2xN, such as 1×4, 1×8, 1×16, 1×32, etc. or smaller, like 1×2, 1×4, etc. for the FBT splitter.

In addition, in order to meet clients’ different requirements, different package are produced by the manufacturers depending on subscriber conditions or cable length, and even the connectors.

Fiberstore offers a integrated product line of these different types of PON splitters. Fiberstore’s fiber optic splitters can be terminated with different kinds of connectors. They are protected from exposure and damage by their packaging. Surrounded by superior cable management, technicians need less time to route fiber in the cabinet, saving operating costs. Available in configurations from 1×2 up to 1×64, the modules can be ordered in adapter port or pigtailed versions. We are specialized in supportting a perfect work for your FTTx solutions.

Types of Fiberstore’s PON splitters:

  • Bare fiber splitter-the PLC splitter without connectors
  • Blockless fiber splitter-PLC Splitter with LC/SC/FC/ST connectors – direct 900μm output
  • Fanout Splitters-PLC Splitter with LC/SC/FC/ST connectors and Fan-out Kit
  • ABS & LGX Splitters-PLC Splitter module with 0.9/2/3mm cable input and output
  • Rack Chassis Splitter- PLC Splitter mounted in patch panel
  • FBT Couplers Splitters

Want a highly splitter product? Want your network working perfectly and stably? Fiberstore is your best alternative! We offers all good quality products with reasonable price. To contact Fiberstore, please log in our website!

The Applications about the Analysis of the Optical Splitter

Function of a fiber optic splitter, as far as I know, it is used to distribute a signal to more than one fiber optical receiver, such as in DVB-T services, because of that can reduce the RF performance of the analogue fiber optic connection, there is a point i have to explain, RF, just Radio Frequency, it is usually in telecommunication industry. In fact, we are bound to say that that it does offer the advantage of a reduction in the number and therefore cost of optical transmitters. And relative, multimode fiber splitter distributing a signal from a single source to multiple destinations offers a significant performance advantage over the use of optical splitters. The exponential increase in demand for bandwidth is forcing access networks to extend the amount of bandwidth they can support. Traditionally based on “static” allocation of time slots per user (or TDM) and passive optical splitters, these systems are struggling to keep pace with the rise in line-rate as it cuts away link budget and therefore splitting ratio and network reach. One attractive alternative for passive splitting is the point of wavelength division.

optical splitter module

We know that fiber optical splitter are available in a number of split rations, they are characterised by the inherent loss associated with the split ratio, added to a excess loss that depends on the design and construction of the splitter and the optical splitters themselves are very compact typically 65 x 15 x 15 mm, and split rations of 1×2,1×4, 1×8, 1×16 optical splitters are examined and compared with a straight through 1×1 system. Optical losses quoted are typical of readily available optical splitters. There are two techniques for manufacturing Splitters: Fused Biconical Taper (FBT splitter) and Planar Lightwave Circuit (PLC splitter). A 1×2 FBT splitter is made in precisely fusing two fibers together. Higher split ratios are obtained by cascading multiple 1×2 splitters. A PLC splitter consists of a microscopic optical circuit that is typically etched in silicon.

application

We fiberstore have some branches in Europe and US, of course some of the Asian regions, probably only suitable solution for high bandwidth demand with a long reach is using optical cable to customers (FTTx). One of the ways is using some type of Passive Optical Network (PON), such as ftth splitter. Gigabit PON (GPON) is the most often type used by European and US providers (in addition to APON and BPON) while providers in Asia predominantly use EPON/GePON. Probably only suitable solution for high bandwidth demand with a long reach is using optical cable to consumers (FTTx). One of the approaches is using some type of Passive Optical Network (PON). Gigabit PON (GPON) is the most often type used by European and US providers (in addition to APON and BPON) while providers in Asia predominantly use EPON/GePON. At this point, the splitting device simply divides the optical power into N separate paths to the subscribers. The number of splitting paths can vary from 2 to 64. From the optical splitter, individual single-mode fiber strand run to each user (home, businesses, etc.). Branches components of a fiber optic communications network, experimental fiber optic devices and any other application requiring highly reliable splitting combining of optical lines. The optical fiber transmission span from the central office to the each user can be up to 20km. Fiberstore provides devices to solve this problem. If you have the needs. Fiberstore will be your choice.

Introduction To Fiber Optic Couplers

A fiber optic coupler is a device used in fiber optic systems with single or more input fibers and single or several output fibers, which is different from WDM  devices. WDM multiplexer and demultiplexer divide the different wavelength fiber light into different channels, while fiber optic couplers divide the light power and send it to different channel.

Bandwidth
Most types of couplers work only in a limited range of wavelength (a limited bandwidth), since the coupling strength is wavelength-dependent (and often also polarization-dependent). This is a typical property of those couplers where the coupling occurs over a certain length. Typical bandwidths of fused couplers are a few tens of nanometers. In high-power fiber lasers and amplifiers, multimode fiber couplers are often used for combining the radiation of several laser diodes and sending them into inner cladding of the active fiber.

Structure
A basic fiber optic coupler has N input ports and M output ports. N and M typically range from 1 to 64. M is the number of input ports (one or more). N is the number of output ports and is always equal to or greater than M. The number of input ports and output ports vary depending on the intended application for the coupler.

Light from an input fiber can appear at one or more outputs, with the power distribution potentially depending on the wavelength and polarization. Such couplers can be fabricated in different ways:
Some couplers use side-polished fibers, providing access to the fiber core;
Couplers can also be made from bulk optics, for example in the form of microlenses and beam splitters, which can be coupled to fibers (“fiber pig-tailed”).

Types
Fiber optic couplers can either be passive or active devices. Passive fiber optic couplers are simple fiber optic components that are used to redirect light waves. Passive couplers either use micro-lenses, graded-refractive-index (GRIN) rods and beam splitters, optical mixers, or splice and fuse the core of the optical fibers together. Active fiber optic couplers require an external power source. They receive input signals, and then use a combination of fiber optic detectors, optical-to-electrical converters, and light sources to transmit fiber optic signals.

Types of fiber optic couplers include optical splitters, optical combiners, X couplers, star couplers, and tree couplers. The device allows the transmission of light waves through multiple paths.

Fused couplers are used to split optical signals between two fibers, or to combine optical signals from two fibers into one fiber. They are constructed by fusing and tapering two fibers together. This method provides a simple, rugged, and compact method of splitting and combining optical signals. Typical excess losses are as low as 0.2dB, while splitting ratios are accurate to within ±5 percent at the design wavelength. The devices are bi-directional, and offer low backreflection. The technique is best suited to singlemode and multimode couplers.

Choices for fiber optic coupler also include Single window narrow band, Single window Wide band, and Dual window Wide band fiber optic coupler. Single window fiber optic coupler is with one working wavelength. Dual window fiber optic coupler is with two working wavelength. For Single mode fiber, is optimized for 1310 nm and 1550 nm; For Multimode fiber, is optimized for 850 nm and 1310 nm.