The fiber optic splitter is also referred to as optical splitter, which is an integrated waveguide optical power distribution device. It plays an important role in passive optical network (EPON, GPON, BPON, FTTX, FTTH and so on) by allowing a single PON interface to be shared among many subscribers. To achieve this, it is designed to split an incident light beam into two or more light beams and couple the light beams to the branch distribution as an optical fiber tandem device, which has the function to maximize the performance of network circuits.
How Optical Splitter Works?
In general, a optical splitter has many input and output terminals to attain the branch of the light beams and maximize the functionality of optical network circuits. The passive optical splitter can split, or separate, an incident light beam into several light beams at a certain ratio. As a simple example, Figure 1 shows how optical splitter with 1x4 split configurations can separate an incident light beam from a single input fiber cable into four light beams and transmit them through four individual output fiber cables. For instance, if the input fiber optic cable carries 1000 Mbps bandwidth, each user in the end of output fiber cables can use the network with 250 Mbps bandwidth.
As for the optical splitter with 2x64 split configurations, it is more complicated than the optical splitter with 1x4 split configurations. There are two input terminals and sixty-four output terminals in the optical splitter with 2x64 split configurations. Its function is to split two incident light beams from two individual input fiber cables into sixty-four light beams and transmit them through sixty-four light individual output fiber cables.
What should be noted is that the ejected light beams may or may not have the same optical power as the incident light beam. The designer would better to take it into consideration when designing the passive optical networks.
Optical Splitter Types Classified by Package Style
The optical splitter can be terminated with different forms of connectors, and the primary package could be box type or stainless tube type. Fiber optic splitter box is usually used with 2mm or 3mm outer diameter cable, while the other is normally used in combination with 0.9mm outer diameter cables. Besides, it has variously different split configurations, such as 1x2, 1x8, 2x32, etc. With the development of the optical splitter manufacturing technology, the fiber optic market can support the high-technical splitter used in the network where the split configurations are 2x64 or larger at present.
Optical Splitter Types Classified by Transmission Medium
According to the different transmission medium, there are single mode optical splitter and multimode optical splitter. For multimode ones, the phrase implies that the fiber is optimized for 850nm and 1310nm operation. For single mode ones, the phrase means that the fiber is optimized for 1310nm and 1550nm operation. Meanwhile, based on working wavelength difference, there are single window and dual window optical splitters. The single window fiber optic splitter is to use one working wavelength, while the dual window fiber optic splitter is with two working wavelengths.
Optical Splitters Types Classified by Manufacturing Technique
On the basis of different manufacturing technique, there are two fiber optic splitter types, which are popularly used nowadays. One is the traditional fused type optical splitter, fused biconic tapered (FBT) splitter, which features competitive prices; and the other is planar lightwave circuit (PLC) splitter, which has compact size and suits for high-density applications. Both of them have the advantages and can be used in different applications.
Fused Biconic Tapered (FBT) Optical Splitters
The FBT splitter (See Figure 2) is fabricated by the traditional technology with over 20 years history. Its manufacturing technique is relatively mature and the manufacturing cost is lower than PLC splitter, so that the FBT optical splitter can be deployed in a cost-effective manner in today’s fiber optic market.
In the manufacturing process of FBT splitter, there are two or more fibers placed closely together, typically twisted around each other and fused together by applying heat 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. Meanwhile, there is a signal source controls the desired coupling ratio to meet the requirements in applications.
Nowadays, FBT splitters are widely used in passive optical networks, especially in the network where the split configuration is not larger than 1x4. In fact, there is a slight drawback of FBT splitter, the split configuration. In details, if more than four splits are required, multiple FBT splitters can be spliced together in concatenation to multiply the amount of splits available, like a tree splitter. By using this design, the package size increases due to multiple FBT splitters and the insertion loss also increases with the additional splitters. Therefore, if high split counts are needed, small package size and low insertion loss are also required, you are suggested to choose a PLC splitter, instead of the FBT splitter.
Planar Lightwave Circuit (PLC) Optical Splitters
With a more recent technology, the PLC splitter (See Figure 3) provides a better solution for applications with larger split configurations. Clearly different from the manufacturing technique of FBT splitters, in the manufacturing process of PLC optical splitters, the waveguides are fabricated by using lithography onto a silica glass substrate, which allows for routing specific percentages of light. As a result, the PLC splitter offers very accurate splits with minimal loss in an efficient package.
With the rapid growth of FTTx worldwide, the requirement for larger split configurations (1x32, 2x64, etc.) in these networks has also grown in order to serve mass subscribers. Due to its performance benefit of larger split configurations, the PLC splitter is more commonly used in the network where the split configuration is larger than 1x4.