The dynamic range of OTDR's relationship with optical fiber testing distance

the OTDR dynamic range is the initial backscatter level and noise level of the dB difference, is one of the main performance index, it determines the maximum of the fiber length measurement. Linear dynamic range, the greater the curve, the better, the longer the measurable distance

fiber refers to OTDR test distance can monitor the length of the cable. By the dynamic range of the OTDR, optical device's intervention loss, fiber optic cable transmission loss, optical fiber connectors ( Mechanical joints, welding joints) Factors such as the loss of decision; Need a calculated and determined according to the actual circumstances of the project.

monitoring distance calculation formula is as follows:

one

m: optical fiber testing system monitoring the maximum length

p: the dynamic range of the OTDR module ( If an OTDR dynamic range is: 1310 band 38 db, 1550 band 36 db, generally 1550 is lower than 1310 db)

Ac: loss of intervention, OTDR, optical switch, WDM, filter and other equipment involved in loss and

Af: fiber attenuation coefficient ( dB /公里) 。 In general single mode fiber in 1310 nm band per kilometer loss is about 0. 33 db /公里; In the 1550 nm band per kilometer loss is about 0. 20 db /公里。

As: light attenuation system (average fusion splicing dB /公里)

Mc: optical fiber cable line surplus degrees ( dB)

Ma: precision surplus degrees ( dB)

value of variables in a formula:

p provided by the system supplier ( As an OTDR dynamic range is 38/36 db)

Af values provided by the cable manufacturer, if you can't provide the average loss when 1625 nm, alternative cable in average loss at the time of 1550 nm.

value As per 2 km a fusion splicing fiber optic cable, each fusion splicing attenuation of 0. 08 db calculation, As 0. 04 db

Ma values of 10 db.

Mc cable line surplus degrees, to ensure that monitoring results accurate values of 3 db.

the calculation of Ac to OTDR, optical switch, WDM, filter, mechanical joint in consumption of wear and tear.

for optical cable monitoring distance calculation, all items need to be first to data generation into the formula, then according to the situation in the project must be empirical correction, make up for the gap between ideal and reality. Of course, the above data is not absolute, that link node number and link parameters such as the intervention of loss are highly correlated.