A Fiber Optic splitter

Introduction:

The optical splitter (FIBEROPTICSPLITTER), also known as the splitter, is one of the most important passive components in the fiber link. It is a device for splitting and combining light energy. It distributes the light energy transmitted in one fiber to two or more fibers according to a predetermined ratio, or combines the light energy transmitted in multiple fibers into one fiber. Commonly used M×N to represent a branch The device has M inputs and N outputs.

 

Types of:

The optical splitter can be divided into a fusion taper type (FUSEDFIBERSPLITTER/FBTSPLITTER) and a planar waveguide type (PLCSPLITTER) according to the splitting principle.

Introduction to the fusion taper optical splitter:

The fused-tapered optical splitter is to disturb two or more optical fibers of the coating layer by a certain method, melt under high temperature heating, and simultaneously stretch to both sides, and finally form a double in the heating zone. A special waveguide structure in the form of a cone can obtain different split ratios by controlling the angle of twist of the fiber and the length of the stretch. Finally, the taper area is solidified on the quartz substrate with a curing gel and inserted into a stainless copper tube.

 

Introduction to Planar Waveguide Optical Splitter:

The planar waveguide optical splitter is fabricated by a dielectric or semiconductor process (lithography, etching, development, etc.), and an optical waveguide is formed on the medium or the semiconductor substrate to realize a branch distribution function, and the optical waveguide array is located on the upper surface of the chip, and the branching function Integrated on the chip, that is, the shunt is implemented on one chip, and then the multi-channel fiber array of the input end and the output end are respectively coupled and packaged at both ends of the chip.

 

Planar waveguide optical splitter classification:

1, bare fiber PLC splitter

2, micro-tube type PLC optical splitter

3. PLC optical splitter with splitter

4, ABS box type PLC optical splitter

5, LGX box type PLC optical splitter

6, micro-insertion type PLC optical splitter

7, tray type PLC optical splitter

8, rack-mounted PLC optical splitter

 

Advantages of a planar waveguide optical splitter:

(1) Loss is not sensitive to the wavelength of light and can meet the transmission needs of different wavelengths.

(2) The splitting is uniform, and the signal can be evenly distributed to the user.

(3) Compact structure and small size, it can be directly installed in various existing transfer boxes without leaving a large installation space.

(4) There are many single-channel shunt channels, which can reach more than 32 channels.

(5) The multi-channel cost is low, and the more the number of branches, the more obvious the cost advantage.

 

Disadvantages of planar waveguide optical splitters:

(1) The device manufacturing process is complicated and the technical threshold is high. At present, the chip is monopolized by several foreign companies, and there are few enterprises capable of large-scale packaging production in China.

(2) Relatively high cost compared to fused taper splitters, especially at low channel splitters

 

Advantages of the fusion cone optical splitter:

(1) The taper coupler has more than 20 years of history and experience. Many equipments and processes only need to be used. The development cost is only a few tenths or even a hundredth of the PLC.

(2) The raw materials are only available in quartz substrates, optical fibers, heat-shrink tubing, stainless steel tubing and less glue, totaling no more than one US dollar. The investment depreciation of machines and instruments is less, 1 × 2, 1 × 4 Equal low channel splitters are low cost.

(3) The split ratio can be monitored in real time as needed, and an unequal splitter can be made.

 

The main disadvantages are:

(1) Loss is sensitive to the wavelength of light. Generally, the device is selected according to the wavelength. This is a fatal defect in the use of triple play, because the optical signals transmitted in the triple play have various wavelength signals such as 1310 nm, 1490 nm, and 1550 nm.

(2) The uniformity is poor, and the uniformity refers to the amount of change in insertion loss at each output end of the splitter that splits the light. The 1X4 nominal maximum difference is about 1.5dB, and the difference between 1×8 and above is larger, which does not ensure uniform splitting, which may affect the overall transmission distance.

(3) Insertion loss varies greatly with temperature (TDL); insertion loss is the ratio of the output optical power of a port to the optical power of the input. The insertion loss is composed of two parts: one is the additional loss, and the other is the split ratio factor; the split ratio of the device is different, and the insertion loss is also different; therefore, there is no specific specification in the standard.

(4) Multi-channel splitters (such as 1×16, 1×32) are relatively large in size, reliability is also reduced, and installation space is limited.

 

Comparison of the main parameters of the tapered and optical waveguides:

Both devices have their own advantages in terms of performance and price, and both process technologies are constantly being upgraded to overcome their shortcomings. The tapered cone splitter is solving the problems of a small number of disposable taps and poor uniformity; the optical waveguide splitter is also making unremitting efforts to reduce costs. At present, the cost of the two devices above 1X8 is almost the same, with The increased size of the split-channel waveguide splitter is better. 2. How to choose the device to choose these two devices, the key is to consider the use situation and the needs of users. In some applications where the volume and optical wavelength are not very sensitive, especially in the case of few shunts, it is more affordable to use a taper optical splitter. For example, the independent data transmission uses a 1310nm taper splitter, and the TV video network can be used. Select the 1550nm taper type splitter; in the case of three-in-one, FTTH and other optical transmissions requiring multiple wavelengths and more users, optical waveguide splitters should be used. At present, most domestic companies use taper splitters for FTTH test networks. This is because many designers are not familiar with PLC devices, and few companies in China produce such devices. The market for true commercial operation of FTTH in Japan and the United States almost exclusively uses planar optical waveguide splitters.

 

Optical splitter specifications Insertion loss:

The insertion loss of an optical splitter is the number of dB of each output relative to the input light loss.

 

Additional loss:

The additional loss is defined as the number of DBs of the total optical power of all output ports relative to the loss of input optical power. It is worth mentioning that for fiber couplers, the additional loss is an indicator of the quality of the device manufacturing process, reflecting the inherent loss of the device manufacturing process. The smaller the loss, the better, which is the evaluation index of the quality of the production. The insertion loss only indicates the output power status of each output port, which not only has the inherent loss factor, but also considers the influence of the split ratio. Therefore, the difference in insertion loss between different fiber couplers does not reflect the quality of the device fabrication. For the 1*N single-mode standard optical splitter, the additional loss is shown in the following table: Number of branches 2345678910111216 Additional loss dB0.20.30.40.450.50.550.60.70.80.91.01.2

 

Split ratio:

The splitting ratio is defined as the output power ratio of each output port of the optical splitter. In system applications, the split ratio is determined by the amount of optical power required by the actual system optical node to determine the appropriate split ratio (except for the average allocation). The splitting ratio of the optical splitter is related to the wavelength of the transmitted light. For example, when one optical branch transmits 1.31 micron light, the split ratio of the two outputs is 50:50; when transmitting 1.5 μm, it becomes 70: 30 (The reason for this is that the optical splitter has a certain bandwidth, that is, the bandwidth of the optical signal transmitted when the splitting ratio is substantially constant). Therefore, be sure to specify the wavelength when ordering the optical splitter.

 

Isolation:

Isolation refers to the ability of an optical path of an optical splitter to isolate optical signals in other optical paths. In the above indicators, the isolation is more important for the optical splitter. In practical system applications, devices with isolation greater than 40 dB are often required, otherwise the performance of the entire system will be affected.

 

Directionality:

In an optical splitter, directionality describes the extent to which light from an output passes through the device to the adjacent output.

 

PDL:

The PDL is defined as the ratio of the maximum power to the minimum power after the different polarization states pass through the device under test, expressed in the form of a pair. In the field of communication and sensing, PDL is a very important indicator, which reflects the sensitivity of a device to different polarization states.

 

The application range of optical splitter:

1. All kinds of optical fiber communication systems 2. Optical fiber LAN, CATV 3. FTTH, FTTB 4. Test equipment, fiber amplifier

 

Optical splitter features:

1. Low loss 2. Low polarization sensitivity 3. Low environmental resistance and low insertion loss