Fiber optic splitter, also called optical splitter, is one of the most important passive devices in optical fiber links.
It is a device to realize the light wave energy shunt.
We Usually use M × N to denote that a splitter has m inputs and N outputs.
According to the principle of optical SPLITTER, optical SPLITTER can divide into FBT SPLITTER and PLC SPLITTER.
The FBT SPLITTER is a method of scrambling two (or more) fiber optic fibers without the coating,
the special waveguide structure with double cones form in the heating region.
At the same time, it melts at high temperatures and stretches to both sides.
Different splitting ratios can be obtained by controlling the twist angle and the stretching length of the fiber.
Finally, a solidified adhesive serves to solidify the taper area on the quartz substrate before inserting it into the stainless copper tube.
To creat PLC SPLITTER，a medium or semiconductor substrate is processed using photolithography, etching, and developing techniques to form an optical waveguide.
The waveguide array position on the upper surface of the chip, where achieve integrated shunt function.
Finally, the input and output ends of the multi-channel fiber array are coupled with the two ends of the chip and packaged.
Introduction to PLC Splitter
Chip
At present, high-quality chip manufacturers have SHIJIA, OLKOPTO, South Korean wooriro, and so on.
Fiber Cable
G657A2 fiber is more expensive than G657A1 fiber in terms of fiber type.
Specification
Regular plc splitter is usually 1 × 2/4/8/32/64/128,
Special Type plc splitter is typically 1 × 3/6/12/24.
Common and Special plc splitter production process is the same, with the main detection wavelength 1310/1490/1550 nm.
Unbalanced fiber optic splitter means 1 × 5/7/9/17 optical splitter.
It uses an output fiber as a cascaded connection to an ordinary PLC, main use in FTTR projects.
The detection wavelength was 1310/1490/1550/1625/1650nm.
Advantages
- The loss is not sensitive to the wavelength of light, so it can meet the transmission needs of different wavelengths.
- The spectrum is even, and the signal can distribute to the user evenly.
- Compact structure, small size, can be directly installed in the existing various transfer box, does not need to leave a large installation space.
- There are many channels for single device, which can reach more than 32 channels.
- The multi-channel cost is low, the more branches, the more obvious the cost advantage. The core technology component of PLC splitter is the chip
Pros and Cons of FBT splitter
Pros
- Taper coupler has more than 20 years of history and experience, many pieces of equipment and technology only need to be used, and the development cost is only a few tens of PLC even a few hundred
- Raw materials are readily available in the form of quartz substrates, fiber optics, heat-shrinkable tubes, stainless steel tubes, and less glue, for a total of less than $1. The investment depreciation cost of machines and instruments is lower, and the cost of low-channel splitters such as 1 × 2,1 × 4 is lower.
- Split ratio can be real-time monitored according to the need, and the unequal splitter can be made.
Cons
- The loss is sensitive to the optical wavelength, so the device should be selected according to the wavelength, which is a fatal defect in the process of using the three-network-in-one because the optical signal transmitted in the three-network-in-one has 1310nm, 1490nm, 1550nm and so on.
- The uniformity is poor, which refers to the change of insertion loss at each output end of the optical splitter. The maximum difference of 1X4 is about 1.5 DB, and the larger difference is above 1 × 8, which can not ensure the uniform spectral distribution and may affect the overall transmission distance.
- Insertion loss (TDL) is the ratio of output optical power to input optical power of a certain port. The insertion loss is made up of two parts: one is the additional loss and the other is the spectral ratio factor; the insertion loss is not the same because the spectral ratio of the device is different, and there is no specification in the standard.
- The volume of the multiplexer (such as 1 × 16,1 × 32) is larger, the reliability is lower, and have limited installation space.
The comparison of FBT splitter and PLC splitter
Each device offers its own advantages in terms of performance and price, and both technologies undergo constant upgrades to address their respective shortcomings.
The FBT splitter is solving the problems such as the small number of one-time taper-pulling and the poor uniformity
PLC splitter are also making great efforts to reduce the cost.
At present, the cost of the two devices is almost the same above 1X8, and the price of planar waveguide splitters will be better with the increase of splitters.
In some applications where the size and wavelength of light are not very sensitive, especially in the case of less branch,
it is more affordable to choose the taper optical splitter.
Such as independent data transmission selection of 1310nm FBT splitter.
The TV video network may choose the 1550nm FBT splitter.
PLC splitters can use in the case of multi-wavelength optical transmission and many users, such as three-in-one, FTTH, and so on.
Specifications for optical splitters
Insertion loss
The insertion loss of a fiber optic splitter is the number of DB of each output relative to the input light loss.
Additional losses
The additional loss is defined as the number of DB of optical power loss relative to the total optical power loss of all output ports.
For optical fiber couplers, the additional loss is an index of the quality of the device manufacturing process.
It reflects the inherent loss of the device manufacturing process.
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 spectral ratio.
Therefore, the difference in insertion loss between different fiber couplers can not reflect the quality of the device.
Beam ratio
The splitting ratio is defined as the output power ratio of each output port of the optical splitter.
In the system application, we should determine the proper split ratio according to the light power of the actual system optical node.
The splitting ratio of an optical splitter depends on the wavelength of the transmitted light,
for example, an optical splitter that transmits 1.31 microns of light has a 50:50 split ratio between the two outputs;
At 1.5 ΜM, it becomes 70:30(this happens because the splitter has a certain bandwidth.
The bandwidth of the optical signal transmitted when the split ratio is constant).
So when you order an optical splitter, you have to specify the wavelength.
Isolation
The degree of isolation refers to the ability of one optical path of an optical splitter to isolate the optical signals in other optical paths.
In the actual system application, the isolation degree often needs to achieve 40 DB above the device.
Otherwise, it will affect the performance of the whole system.
Directionality:
In an optical splitter, directivity describes the effect of incoming light from an output on adjacent outputs.
PDL
PDL is defined as the logarithmic ratio of the maximum power to the minimum power after the different polarization states pass through the device that is measured.
In the field of communication and sensing, PDL is a very important indicator, it reflects the sensitivity of a device to different polarization states.
Applications of optical splitter
1. All types of Fiber-optic communication systems 2. Fiber optic LAN, CATV 3. FTTH, FTB 4. Test equipment, optical fiber amplifier
Features of optical splitter:
2. Low loss 2.1%. Low polarization sensitivity
3. Low insertion loss against environmental change
