The usage of optical coupler and its optimization signal in modified optical time domain reflectometer

In this study, attention was made to measure the length of the fiber and the coefficient of the fiber attenuation utilizing novel configurations. Laser diode source with a fundamental wavelength of (808 ± 10) nm with a maximum power of 50 mW was employed. First measurement utilizes a polarized beam splitter whereas the second measurement utilizes a beam coupler. The laser was launched in pulsed mode with a 75 ns pulse width which delivered approximately 15 mW power into the fiber and the laser source was adjusted to operate in continuous mode with a 50 % duty cycle. A preamplified Si PIN photodetector was used to detect the backscattered light. Later these results were compared with a measurement that utilizes a conventional Anritsu OTDR with a 850 nm wavelength. The length of the fiber obtained is 1313.99 m and shows a deviation of 0.46 % for the first measurement and 1303.89 m with a deviation of 0.38 % for the second measurement. The attenuation coefficient for that fiber is 2.65 dB.km-1 with a deviation of 16.22 % for the first measurement and 2.58 dB.km-1 with a deviation of 13.16 % for the second measurement. An adjustable BK7 glass plate was used for signal optimization in the system. Results show that maximum coupling and also maximum backscattered signal occurs when the BK7 glass window is rotated 35° anticlockwise.