Do you know about optical splitters ?

As with the coaxial cable transmission system, optical network systems also need to be coupled, branching, distribution of optical signals, which requires optical splitter to achieve. Optical splitter, also known as splitter, is one of the most important passive components in the fiber optic link, is a fiber optic splice device with multiple inputs and multiple outputs, commonly used MXN to indicate that a splitter has M inputs and N outputs. Optical splitters used in fiber optic CATV systems are generally 1×2, 1×3 and 1×N optical splitters composed of them.

1. Optical splitter splitting principle

Optical splitter according to the principle can be divided into fused pull cone type and plane waveguide type two kinds of fused pull cone type products are two or more optical fibers for side fusion and become; plane waveguide type is a micro-optical components type products, using photolithography, in the dielectric or semiconductor substrate formation of optical waveguide, to achieve the function of branch distribution. These two types of light-sharing principle is similar, they change the optical fiber by changing the fading field coupling (coupling, coupling length〉as well as changing the fiber radius to achieve different sizes of the amount of branching, and vice versa, can also be more than one way to combine the optical signal into a signal is called a synthesizer. Fused cone type fiber optic coupler because of the production method is simple, inexpensive, easy to connect with the external fiber to become a whole, and can withstand the mechanical vibration and temperature changes, etc., currently becoming the mainstream of the market manufacturing technology.

Molten pull cone method is to remove the two (or two or more) to remove the coating layer of the optical fiber to a certain method of interference, fused under high temperature heating, while stretching to both sides, and ultimately in the heated area of the formation of a double cone in the form of a special waveguide structure, through the control of the optical fiber to twist the angle and the length of the stretching can be obtained by a different proportion of the splitter. Finally pull the cone area with curing adhesive cured on a quartz substrate inserted into a stainless steel tube, which is the optical splitter. This production process because of the curing adhesive thermal expansion coefficient and quartz substrate, stainless steel tube is not consistent, in the ambient temperature changes in the degree of thermal expansion and contraction is not consistent, this situation is likely to lead to damage to the optical splitter, especially the optical splitter placed in the field is more so, which is the optical splitter easy to damage the most important reason. For more road number of splitter production can be composed of more than two splitter.

2.Common technical specifications of optical splitter

(1) Insertion loss

The insertion loss of the optical splitter is the number of dB of each output relative to the input optical loss, and its mathematical expression is:Ai=-10lg Pouti/Pin, where Ai is the insertion loss of the ith output port; Pouti is the optical power of the ith output port; Pin is the value of the optical power of the input.

(2) Additional losses

The additional loss is defined as the DB number of the sum of the optical power of all output ports relative to the input optical power loss. It is worth mentioning that, for fiber optic couplers, the additional loss is an indicator of the quality of the device manufacturing process, reflecting the inherent loss of the device production process, the smaller the better, the better the quality of the production of the assessment indicators. The insertion loss only indicates the output power condition of each output port, not only the factor of intrinsic loss, but also consider the influence of the splitting ratio. Therefore, between different fiber optic couplers, the difference in insertion loss does not reflect the quality of the device production. For 1 * N single-mode standard optical splitter additional loss is shown in the following table.

Number of branches 23 4 56 789 10 11 12 16

Additional loss DB 0.20.3 0.4 0.45 0.5 0.55 0.6 0.7 0.8 0.9 1.0 1.2

ABS Box Type PLC Splitter

(3)Spectral ratio

Split ratio is defined as the ratio of the output power of each output port of the optical splitter, in the system application, the split ratio is indeed based on the actual system optical nodes required by the amount of optical power, to determine the appropriate split ratio (except for the average distribution), the split ratio of the optical splitter and the transmission of the wavelength of the light is related to the wavelength of the light, for example, an optical splitter in the transmission of the light of 1.31 μ m when the split ratio of the two outputs for the split ratio of 50:50; in the transmission of 1.5u m of light, it becomes 70:30 (the reason for this situation, because the optical splitter have a certain bandwidth, that is, the split ratio is basically unchanged when the bandwidth of the transmitted optical signal). Therefore, the wavelength must be specified when ordering an optical splitter.

(4)Isolation

Isolation degree refers to the optical splitter of an optical path on the other optical path of the optical signal isolation ability. In the above indicators, the degree of isolation for the optical splitter is more significant, in the actual system applications often require isolation of more than 40dB devices, otherwise it will affect the performance of the entire system.

In addition, the stability of the optical splitter is also an important indicator of the so-called stability refers to changes in the external temperature, other devices, changes in the operating state of the optical splitter splitting ratio and other performance indicators should remain basically unchanged, in fact, the stability of the optical splitter is entirely dependent on the level of the manufacturer's process, the products of different manufacturers, the quality of the difference between the large. In practical applications, I did encounter a lot of low-quality optical splitter, not only the performance indicators deteriorate quickly, and the damage rate is quite high, as for the fiber optic backbone of the important devices, in the purchase of attention must be paid to the price can not just look at the process level of low optical splitter price is certainly low.

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