Tag Archives: Fiber Optic Coupler

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.

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.

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.

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”).

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.