The optical splitter（PLC Splitter) is a connecting device between multiple input ends and output ends, which can realize the coupling, branching and distribution of optical signals in the optical network system. It is the most important part of the optical fiber link. M×N is often used to indicate that an optical splitter has M input ends and N output ends. The optical splitters used in today's networking are generally 1×2, 1×4 optical splitters. So do you know how much the attenuation of the optical splitter is? How to choose a splitter? And how to use that?

What is the attenuation of the optical splitter? How to calculate?

Four common technical indicators of optical splitters: wavelength, insertion loss, additional loss and splitting ratio. In fact, the most important indicator of a beam splitter is the different light attenuation produced by the beam splitter under a specific splitting ratio. Under the conditions of different splitting ratios, the light attenuation of the beam splitter will not be different. So how to calculate the light attenuation of the optical splitter? The optical attenuation value of the optical splitter = transmit optical power + additional loss + insertion loss + bare fiber loss.

1.Calculation of the splitting ratio of the optical splitter

Formula: ki=Pi/SP*100%

Among them, Pi is the required drive power of each optical link, and SP is the sum of the required drive power of each optical link carried by the laser.

Note: In actual use, the manufacturer has indicated the splitting ratio, such as 80% for one point two: 20% or 70%: 30%; one point three for 70%: 15%: 15%; one point four for 70%: 10 %: 10%: 10%.

2.Additional loss calculation

In the actual operation process, the additional loss value can be measured. It is only necessary to perform the value detection and recording in accordance with certain operating specifications to classify the different links.

Generally, the loss of 1×N single-mode standard optical splitter is as follows:

3. Insertion loss calculation

Formula: IL=-10lg(Po/Pi)
Po is the optical power at the output end, and Pi is the optical power at the input end.
Note: In the formula, Po/Pi is equivalent to the splitting ratio of the optical splitter, namely: IL=-10lg(ki). For example, there is a two-to-two splitter, which means that the splitting ratio is 20%:80%. The theoretical value of the insertion loss of the 20% split optical link is -10lg (20%), which is approximately equal to 6.99dB.

4. Bare fiber loss calculation

In actual operation, this value does not need to be calculated, and there is a certain reference standard. Strictly refer to the numerical standard, measure the loss values of different wavelengths, and determine the final loss value

Note: Active connector attenuation: generally 0.5dB each.

What are the types of splitters? How to choose?

The optical splitter can be divided into two types: fused tapered optical splitter (FBT) and planar waveguide (PLC) optical splitter according to different manufacturing processes. Among them, the planar waveguide optical splitter (PLC) is widely used in FTTx and PON. The fusion tapered beam splitter is formed by fusion splicing two or more optical fibers on the side; the planar waveguide beam splitter (PLC) is a micro-optical component type product that uses photolithography technology to form an optical waveguide on a dielectric or semiconductor substrate. Realize branch assignment function. The splitting principles of these two types of optical splitters are similar. They both achieve different branch amounts by changing the evanescent field coupling between the fibers (coupling degree, coupling length) and changing the fiber radius.

PLC is divided into 1×2, 1×4, 1×8, 1×16, 1×32, 1×64 and other optical splitters according to the difference of light splitting ratio. [Note: On the semiconductor engraved board, the "Y"-shaped waveguide coupler is engraved by photolithography technology, and these "Y" waveguides are connected together to form a step-by-step light splitting, which can realize 1×2, 1×4, 1× 8. Split ratio of 1×16, 1×32, 1×64, etc. ]

How to choose among the many types of optical splitters mentioned above? We can first determine the application situation and choose the appropriate splitter according to the actual needs. For example, in the application where there are few branches and the light wavelength is not sensitive (that is, only 1×2 or 1×4 is enough), choose FBT Splitter; if so In FTTH and other applications that require multiple wavelengths (that is, 1×4 or more), choose PLC Splitter because the PLC Splitter has the same light splitting and uniform channels.

Principles and planning for the use of optical splitters

The split ratios of commonly used splitters are 1:2, 1:4, 1:8, 1:16, 1:32, 1:64. If necessary, you can also choose 2:N optical splitter or non-uniform splitting. Splitter. When configuring the optical splitter, the maximum utilization rate of each PON port and optical splitter of the equipment must be considered. According to the user distribution density and distribution form, the optimal optical splitter combination mode and suitable installation position must be selected. There are two principles for the use of optical splitters: one is to use first-level splitting as much as possible, and the other is that the number of splitting levels does not exceed two. There are three reasons for the use of first-level splitting: first, it can maximize the utilization of PON; second, it is convenient to diagnose faults; third, the system has high reliability. So how to place the splitter?

(1) The first-level splitting method is adopted. When the optical splitter is in the resident network, the splitter can be installed indoors or outdoors. The indoor installation locations include the central computer room of the community, the weak current well in the building, and the floor line box. The upper connecting optical cables of the optical splitter can come from three ways, namely, the first-level optical junction box, the second-level optical junction box, or the optical fiber splitter box. This method is mainly suitable for the situations where the built communities are large in scale and high in user density, such as high-rise residential buildings.

(2) If the secondary optical splitting method is adopted, the optical splitter can be installed on the backbone layer or the user distribution cable layer. In the backbone layer, the splitter can be installed in the primary optical junction box, secondary optical junction box or Inside the optical fiber distribution box. This method is suitable for situations where users are relatively scattered and for newly-built user optical cable networks.

How to use the Optical Splitter?

With the large-scale advancement of fiber to the home (FTTH) in China, the application of various optical passive products has developed rapidly. As the most core passive optical device in the construction of fiber to the home (FTTH), optical splitters are used to ensure communication links. Important equipment for normal transmission. So how are optical splitters used in fiber to the home (FTTH) cabling?

At present, the primary and secondary spectroscopy methods are often used in engineering. For the first-level optical splitting method, the use of the optical splitter is generally divided into four situations: one is placed in the central office computer room; the second is placed in the cell computer room; the third is placed in the cell optical transfer box; the fourth is directly placed in the corridor. For the second-level splitter, the use of the splitter is generally divided into three situations: one is that the first-level splitter is placed in the central office's machine room, and the second-level splitter is placed in the optical crossover box; the second is that the first-level splitter is placed next to the road. In the large-capacity optical crossover box, the secondary optical splitter is placed in the community optical crossover box; the third is that the primary optical splitter is placed in the residential optical crossover box, and the secondary optical splitter is placed in the corridor.