When light is injected into an optical fiber, some of it is scattered within the optical fiber to the opposite end of the light‘s path. This is called backscattered light. Each optical fiber has its own backscattered light value, or level. Since the connection loss for fibers with different backscatter levels varies according to the measurement direction, correct loss assessment requires measurement from both ends.
For example, a fiber whose backscatter level is -60 dB is connected to a fiber of -55 dB at a loss of 3 dB:
The correct loss value is the average of the following:
The loss of “gainer” event 1 measured from End A: -2 dB
The loss of “loser” event 1 measured from End B: 8 dB
Therefore, the correct loss = = 3 dB
By averaging the values measured from both ends, the backscatter value of the fibers is deducted and the loss of event 1 is corrected. Analysis of two-way measurement in the AQ7280 and AQ1210 is [Advanced Analysis] → [2-Way Trace].