Common Passive Fiber Optical Splitters

Fiber optical splitter, also named fiber optic coupler or beam splitter, is a device that can distribute the optical signal (or power) from one fiber among two or more fibers. Fiber optic splitter is different from WDM(Wavelength Division Multiplexing) technology. WDM can divide the different wavelength fiber optic light into different channels, but fiber optic splitter divide the light power and send it to different channels.

Work Theory Of Optical Splitters

The Optical Splitters “split” the input optical signal received by it between two optical outputs, simultaneously, in a pre-specified ratio 90:10 or 80:20. The most common type of fiber-optic splitter splits the output evenly, with half the signal going to one leg of the output and half going to the other. It is possible to get splitters that use a different split ratio, putting a larger amount of the signal to one side of the splitter than the other. Splitters are identified with a number that represents the signal division, such as 50/50 if the split is even, or 80/20 if 80% of the signal goes to one side and only 20% to the other.

Some types of the fiber-optic splitter are actually able to work in either direction. This means that if the device is installed in one way, it acts as a splitter and divides the incoming signal into two parts, sending out two separate outputs. If it is installed in reverse, it acts as a coupler, taking two incoming signals and combing them into a single output. Not every fiber-optic splitter can be used this way, but those that can are labeled as reversible or as coupler/splitters.

Attenuation Of Fiber Optic Splitter

An interesting fact is that attenuation of light through an optical splitter is symmetrical. It is identical in both directions. Whether a splitter is combining light in the upstream direction or dividing light in the downstream direction, it still introduces the same attenuation to an optical input signal (a little more than 3 dB for each 1:2 split). Fiber optic splitters attenuate the signal much more than a fiber optic connector or splice because the input signal is divided among the output ports. For example, with a 1 X 2 fiber optic coupler, each output is less than one-half the power of the input signal (over a 3 dB loss).

Passive And Active Splitters

Fiber optic splitters can be divided into active and 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.

Passive splitters play an important position in Fiber to the Home (FTTH) networks by permitting a single PON (Passive Optical Network) network interface to be shared amongst many subscribers. Splitters include no electronics and use no power. They’re the community parts that put the passive in Passive Optical Network and are available in a wide range of break up ratios, including 1:8, 1:16, and 1:32.

Optical splitters are available in configurations from 1×2 to 1×64, such as 1:8, 1:16, and 1:32. There are two basic technologies for building passive optical network splitters: Fused Biconical Taper (FBT) and Planar Lightwave Circuit (PLC). FBT Coupler is the older technology and generally introduces more loss than the newer PLC Splitter.

Industrialization of PLC splitter chip technology

Fiber optic communication network has become the cornerstone of today’s world of information transfer. With the further development of the network and market demand for communication bandwidth increases, the entire communication network to the part between the user’s last ten km and last km, the network part is also being optical fiber. FTTH becomes an important direction of the development of fiber optic communication network.

FTTH mainly uses PON network technology, which requires a large number of low-cost optical splitters and other optical passive. Optical splitter device is an integral part of FTTH, and with the promotion of FTTH, there would be a great market demand. The traditional preparation of optical splitter technology is fiber fused biconical taper (FBT) technology. Its characteristics are mature and simple technology. The disadvantage is that the assigned ones too large, and the device size is too large, which causedthe decrease in yield and the rising cost of single channel, shunt reactive stars uniformity will deteriorate. FBT technology based fiber optic splitter preparation techniques have been unable to adapt to the market demand.

As you can see from the perspective of development of optical devices, PLC technology has become a mainstream technology for large-scale preparation of high-performance and low-cost optical splitter. It is the use of PLC technology, to produce the optical splitter chip, coupled with the optical fiber array package, complete the preparation of the optical splitter. Its features are: small size of the device, the cost is relatively low, splitter good uniformity, at the same time, the technical threshold is relatively high, especially for production of more than large ones optical splitter, suitable for mass production. It can ensure that the light emitting device miniaturization, low cost and high performance. Analysis of PLC technology, you can see that the glass-based PLC technology has great advantages in terms of equipment investment, production costs, the optimal choice of production required for fiber-to-the-home, low-cost optical devices such as optical splitter.

International, PLC technology has been widely used in the miniaturization, high-performance optical device fabrication and production, in particular, the optical splitter chip. In China, however, the reality is that we have become a PLC encapsulation big country, but is limited to the optical splitter and optical device fabrication device coupled packaging and downstream industry chain, no one PLC chip Health line, PLC core device chip entirely dependent on imports. Which there is a problem that the core preparation technique of the PLC device lies in the outward, this has resulted in major cost control of the device is limited in the chip at the same time, which also led to the lack of technical support further to the high-end integrated chip development, severe hinder the development of our country in the PLC application.

PLC splitter chip manufacturing process PECVD (plasma enhanced chemical vapor deposition) and FHD (flame hydrolysis deposition) and ion exchange. The former two with the substrate material is a silicon-based silica, and the latter with the substrate material is glass. AWG (arrayed waveguide grating) chip production, Silica optical waveguide splitter chips can be produced on silica on silicon waveguide or glass waveguide. Production by ion exchange glass waveguide PLC chip domestic number of colleges and universities have been conducting research and development, technical appraisal sample has been reached the international advanced level of similar products. The breakthrough of the results from the glass material, preparation equipment, process conditions designed to chip a full range of core technology to master the the buried low loss and low polarization characteristics PLC chip core preparation techniques.

Characteristics of the technology investment, equipment operation and low maintenance costs, simple process conditions, the production of optical passive low transmission loss and polarization characteristics with matching coupling of the fiber loss, environmental stability, and manufacturing costs low, very suitable in need of the PLC production line, can be used for producing low-cost fiber-to-the-home integrated optical splitter chip. Further pilot research and development, to solve adapted to the production of core technology, will be able to achieve your PLC splitter chip mass production.

In fact, in addition to the production of optical splitter chip, glass-based PLC technology R & D production environment with a wide range of other potential applications, for example, can be applied to detect the required light sensor.

Source: FiberStore

Production Process of Fiber Optic Splitter with Advantages and Disadvantages

Fiber optic splitter (optical splitter) is also known as “non-wavelength selective optical branching device”. It is a fiber optic device used to achieve a particular band optical signal power splitter and redistribution.

Optical splitter can be used as a stand-alone device in the OLT node, the light distribution point and the FTTH point. It can also be placed in the central office wiring facilities, the light distribution points and FTTH points within the facility (integrated design or plug-in).

In accordance with the production process, optical splitters are divided into Fused Bi-conical Taper (FBT Splitter) and Planar Lightwave Circuit (PLC Splitter).

FBT Splitter (FBT Coupler)

Fused Bi-conical Taper technique is tied to two or more fibers, and then melted in a cone machine, pull tensile and real-time monitoring of changes in splitting ratio, the splitting ratio to meet the requirements after the end of the melt stretching, and wherein one end of a fiber optic reserved ( The remaining cut off) as the input terminal and the other end a multitude of road outputs. Mature tapering process can only pull 1 × 4. 1 × 4 or more devices, with a plurality of 1 × 2 connected together. Then the overall package in the splitter box.

Advantages
(1) pull taper coupler over twenty years of history and experience, many equipment and processes simply follow the only development funds only a few of the PLC tenth or hundredth of a few
(2) Raw materials only readily available quartz substrate, fiber optics, heat shrink tubing, stainless steel pipe and less plastic, a total of not more than $ 1. Investment in machinery and equipment depreciation costs less, 1 × 2,1 × 4 and other low-channel splitter low cost.
(3) splitting ratio can be real-time monitoring, you can create unequal splitter.

Disadvantages
(1) Loss of light sensitive wavelength ships according to the wavelength selection device, in this triple-play during use is a fatal defect, since the triple play of light transmitted signal 1310nm, 1490nm, 1550nm, and other multiple-wavelength signal.
(2) poor uniformity, 1×4 nominal about 1.5dB away, 1 × 8 or more away from larger, can not ensure uniform spectroscopic, which may affect the overall transmission distance.
(3) Insertion loss varies with temperature variation is greater (TDL)
(4) multi-demultiplexer (e.g., 1 × 16,1 × 32) volume is relatively large, the reliability will be reduced, the installation space is restricted.

PLC Splitter

Planar waveguide technology is the optical waveguide branching device with a semiconductor production process. The branching function is completed on the chip. On one chip to achieve up to 1X32 splitter, then, at both ends of the chip package input terminal and an output terminal respectively coupled multi-
Channel optical fiber array.

Advantages
(1) The loss of transmission is not sensitive to the wavelength of light, to meet the transmission needs of different wavelengths.
(2) spectroscopic uniform signal can be uniformly allocated to the user.
(3) compact structure, small size, can be installed directly in the existing junction box, no special design leave a lot of space for installation.
(4) only a single device shunt channel can achieve much more than 32 channels. (5) The multi-channel, low cost, stars ones more and more obvious cost advantages.

Disadvantages
(1) Device complex production process, high technical threshold, the chip is several foreign companies to monopolize domestic bulk package production companies only Borch rarely several.
(2) relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.

Source: http://www.fiberstore.com/

PLC Splitter Production and Packaging

With the recovery of optical fiber communication industry and the development of FTTX, the spring of fiber optic splitter market is coming.

There are two types of optical splitter, which are Fused fiber splitter and PLC splitter. PLC splitter is a hot research today, with a good prospect of application. PLC splitter package, however, is the difficulty in manufacturing.

The PLC splitter Package refers to the planar waveguide splitter on the light guide path (waveguide) with the fiber in the fiber array aligned one by one, and then stick with specific adhesive (such as epoxy glue) together with the technology. Wherein the alignment accuracy of the PLC splitter and an optical fiber array is the key technology. PLC splitter package involves a six-dimensional optical fiber array and optical waveguides in close alignment difficult. When the manual, the drawback is the low efficiency, poor reproducibility, human factors and is difficult to achieve large-scale production.

PLC splitter Production
PLC splitter using semiconductor technology (lithography, etching, developing technology) production. Multi-channel optical fiber array and the optical waveguide array is located on the upper surface of the chip, branching function is integrated on-chip is a chip on the splitter 1,1; Then, the ends of the chip, respectively coupling the input terminal and an output terminal package.

Compared with Fused Splitter, PLC splitter has these advantages: (1) loss wavelength is not sensitive to light, to meet the different wavelengths of the transmission needs. (2) spectroscopic uniform signal can be uniformly allocated to the user. (3) compact structure, small size, can be installed directly in the various existing junction box, without leaving a lot of space for installation. (4) only a single device shunt channel can achieve much more than 32 channels. (5) The multi-channel, low cost, stars ones more and more obvious cost advantages.

At the same time, the main drawback of the PLC splitter: (1) device fabrication process complexity, high technical threshold, the chip by several foreign companies to monopolize the domestic bulk package produced by very few companies. (2) relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.

PLC splitter Packaging Technology
PLC splitter package process includes coupling alignment and bonding operations. Coupling of the PLC splitter chip and the optical fiber array is aligned with both manual and automated, and they depend on the hardware with the six-dimensional precision trimming frame, the light source, power meter, microscopic observation system, while the most commonly used are self-aligned , it is through the optical power feedback closed-loop control is formed, and therefore high coupling efficiency docking accuracy and docking.

PLC splitter has 8 channels and each channel must be accurately aligned to ensure that the relative position between the respective channels due to the manufacturing process of the waveguide chip and an optical fiber array (FA), so only the PLC splitter and the first channel of the FA and 8-channel simultaneous alignment can ensure that other channel aligned, thus reducing the complexity of the package. The most important in the packaging operation at the technical difficulty is the highest coupling alignment operation, it comprises two steps First Harmonic precise alignment. First tune the purpose is to enable the waveguide to light through; the purpose of precise alignment is precise positioning of the completion of the preferred optical power of the coupling point, and it is realized by the program to search the maximum optical power.