Optical Fiber Splitter
Optical fiber splitter is a device used to split and combine light wave energy. It distributes the light energy transmitted in one optical fiber to two or more optical fibers according to a predetermined ratio, or combines the light energy transmitted in multiple optical fibers into one optical fiber.
(1) Insertion loss
The insertion loss of a fiber splitter refers to the dB number of each output relative to the input optical loss. Its mathematical expression is: Ai=-10lg Pouti/Pin, where Ai refers to the insertion loss of the i-th output port; Pouti is The optical power of the i-th output port; Pin is the optical power value of the input end.
(2) Additional loss
The additional loss is defined as the DB number of the total optical power of all output ports relative to the loss of the input optical power. It is worth mentioning that for optical fiber couplers, 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, and it is an evaluation indicator of the quality of the manufacturing. The insertion loss only indicates the output power status of each output port, not only has the inherent loss factor, but also considers the effect of the splitting ratio. Therefore, the difference in insertion loss between different fiber couplers does not reflect the quality of the device manufacturing. For 1*N single-mode standard fiber optic splitter, the additional loss is shown in the following table: Number of branches 2 3 4 5 6 7 8 9 10 11 12 16 Additional loss DB 0.2 0.3 0.4 0.45 0.5 0.55 0.6 0.7 0.8 0.9 1.0 1.2
(3) Splitting ratio
The splitting ratio is defined as the ratio of the output power of each output port of the optical fiber splitter. In system applications, the splitting ratio is indeed based on the optical power required by the actual system optical nodes to determine the appropriate splitting ratio (except for the average distribution). The splitting ratio of the fiber splitter is related to the wavelength of the transmitted light. For example, when an optical splitter transmits 1.31 micron light, the splitting ratio of the two output ends is 50:50; when transmitting 1.5μm light, it becomes 70: 30 (The reason for this situation is that the optical fiber splitter has a certain bandwidth, that is, the bandwidth of the transmitted optical signal when the splitting ratio is basically unchanged). Therefore, the wavelength must be specified when ordering a fiber splitter.
Isolation refers to the ability of an optical path of a fiber splitter to isolate optical signals in other optical paths. Among the above indicators, the isolation is more significant for the optical fiber splitter. In actual system applications, devices with an isolation of more than 40dB are often required, otherwise it will affect the performance of the entire system. In addition, the stability of the fiber splitter is also an important indicator. The so-called stability means that when the external temperature changes and the working status of other devices changes, the splitting ratio and other performance indicators of the fiber splitter should basically remain unchanged. In fact, the stability of the optical fiber splitter depends entirely on the manufacturer's technological level, and the quality of products from different manufacturers is quite large. In practical applications, I did come across many low-quality optical fiber splitters. Not only did their performance indicators deteriorate quickly, but the damage rate was quite high. For important components used in optical fiber trunk lines, we must pay attention to them when purchasing them. Price, the price of optical branch with low technology level is definitely low.
In addition, uniformity, return loss, directivity, and PDL all occupy a very important position in the performance indicators of optical fiber splitters.