As fiber optic link becomes more and more acceptable by average consumers, Passive Optical Network (PON) systems are more widely deployed in common homes. Fiber optic splitter is an indispensable passive optical device in PON systems. Optical splitters can be divided into Fused Biconical Taper (FBT) splitter and Planar Lightwave Circuit (PLC) splitter. PLC splitter is newer than FBT splitter and is also the focus of this post.

What Is PLC Splitter?

PLC splitter, also called Planar Waveguide Circuit splitter, is used to divide one or two light beams to multiple light beams uniformly or combine multiple light beams to one or two light beams. It is a passive optical device with many input and output terminals, especially applicable to PON (EPON, GPON, BPON, FTTX, etc.) to connect the MDF (main distribution frame) and the terminal equipment and to branch the optical signal. Fiber PLC splitter provides a low cost light distribution solution with high stability and reliability. PLC splitters can offer a splitting ratio up to 1×64, which is generally higher than the splits of FBT splitter. If you want to figure out the difference between FBT splitter and PLC splitter.

Fiber Optic PLC Splitter Manufacturing Technology

PLC splitter is based on Semiconductor technology. As its name shows, PLC splitters are manufactured by planar waveguide circuit technology. PLC splitter design consists of one optical PLC chip and several optical arrays depending on the output ratio. The optical arrays are coupled on both end of the PLC splitter chip.

Figure 1: PLC splitter design consists of PLC splitter chip and fiber arrays.

PLC chip is one key component of a fiber PLC module. It is available in 1xN (N=2, 4, 8, 16, 32, 64) and 2xN (N=2, 4, 8, 16, 32, 64) splitting ratios. The figure below shows the typical design of a 1×8 PLC splitter chip.

Figure 2: A typical PLC splitter chip design.

How Does PLC Splitter Work?

PLC splitter is widely installed between the PON Optical Line Terminal (OLT) and the Optical Network Terminals/Units (ONTs/ONUs) that the OLT serves. The single fiber link coming from the Central Office (CO) OLT is connected with the input of a splitter and is split into given numbers of fibers leaving the splitter. The number of the outputs in the PLC module determines the number of splits. PLC splitters can be used in centralized PON architecture or distributed architecture. In a centralized PON architecture, generally a 1×32 PLC splitter is used in the Central Office. In a distributed PON architecture, a 1×4 PLC splitter is firstly directly connected to an OLT port in the Central Office, then each of the four fibers is routed to an outside plant terminal/enclosure box that houses a 1×8/1×4 PLC splitter. The illustration is as follows:

Figure 3: How PLC splitter works in PON centralized and distributed architectures.

Different Types of PLC Splitters

Fiber optic PLC splitter can be categorized by the PLC splitter chip they use, meaning there are 1xN and 2xN PLC splitters, such as 1×4, 1×8, 1×16, 2×32, 2×64, etc. Installers can choose different input and output numbers depending on subscriber conditions or cable length.

In addition, PLC splitter manufacturers produce different packages of PLC modules to meet clients’ needs in various scenarios, including small size PLC splitter that need to be used in terminal box and big size rack mounted PLC that can be installed in racks. Actually the package of PLC splitter is a key factor to be considered in purchase. Here are some common types of PLC splitters in the market.

PLC Splitter Type	Characteristics
Bare Fiber PLC Splitter	-Simplest PLC splitter type. -All ends are bare fibers (0.9/2.0/3.0µm). -Can be spliced freely according to the applications. -Requires the least space during cabling.
Blockless PLC Splitter	-Resembles bare fiber PLC splitter, but has fiber optic connectors. -Uses stainless tube package for the PLC splitter chip.
Fanout PLC Splitter	-Generally uses 0.9mm buffer fiber. -Adds a length of ribbon fiber terminated with fanout kit behind the PLC split chip.
ABS PLC Splitter	-Uses ABS plastic box to hold the PLC splitter chip. -Input fiber and output fibers are arranged on the same plate of the ABS box. -Can be installed in standard 19” rack unit/enclosure.
LGX Box PLC Splitter	-The whole PLC splitter is housed in a metal box and the fiber optic adapters for both input and output fibers are on its front panel. -Can be used stand alone or be installed in the standard rack unit/enclosure.
Mini Plug-in PLC Splitter	-Looks like LGX box PLC splitter but usually uses ABS material box. -Can be used in outdoor fiber distribution box in FTTX.
Rack Mount PLC splitter	-Uses a standard 19” design package. -Can be installed in server racks in data centers or server rooms. -Suitable for high density cabling, up to 64 output ports in 1U pack.

Conclusion

Fiber optic PLC splitter is a low cost fiber distribution solution in passive optical networks. PLC splitter design is based on planar waveguide circuit technology, and the key component PLC splitter chip offers high optical performance. The splitting ratios of PLC splitters can be 1×2 to 64 or 2×2 to 64, which can meet different subscriber numbers and PON architectures in GPON, EPON, FTTX applications. Besides, the package of PLC splitter can be either small form factor or standard 19” design to fit various implementing environments. If you want to learn about full categories of fiber optic splitters, you can read article: What Is a Fiber Optic Splitter?