Analysis of Experimental Values of Bend Loss by OTDR

DOI : 10.17577/IJERTCONV3IS10092

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Analysis of Experimental Values of Bend Loss by OTDR

Ravi Garg1, Rakesh Joon2, Satish Kumar3

1, 2, 3 Department of Electronics and Communication Engineering, Ganga Institute of Technology & Management Kablana,

Jhajjar, India

Abstract- In this paper, showed the measurement of bend loss in single mode fiber and multimode fiber in different bend radius at different wavelength by using OTDR and compares the value of bend loss of single mode fiber with standard paper and also performed reduce the bend loss at particular radius .

Keywords : Single mode cable, multi mode cable, power meter, OTDR.


    The optical fiber bending loss is created by that light fail to comply with this requirement of total internal reflection. In other word, bending an optical fiber introduce a loss in light power or attenuation. This is one of the major causes of the total attenuation that light experiences while propagating through an optical fiber. The result is failure to achieve total internal reflection in the bent fiber .Which means that some portion of the beam is escaping from the core of the fiber .Hence the power of the light arriving at its destination will be less than the power of light emitted into the fiber from a light source.

    Fig.1. Schematic diagram of the optical set-up for measuring bendingloss of the fiber.

    Although optical fiber bending loss goes against signal transmission. In this paper, study the trend of change of bending loss Characteristics in different mode field diameter fiber and under diverse condition, such as tension /pressure and different temperature. In real, Measurement of the bending loss reflects power distribution in optical fiber. We may measure using by Optical Power Meter and OTDR in such experiments. I choose OTDR in my research and Figure 2 shows the course of measuring. There is OTDR

    at the left. In addition, OTDR works, based on Fresnel reflection and Rayleigh scattering.


    We first considered the bending loss of different radius at different angle of single and multimode fiber. In single mode has a narrow core so one mode can pass and multimode fiberhas large core compare to single mode. So different light ray can be pass and compare the bend loss of single mode fiber with multimode fiber at different angle. I analyzed the relationship between them. Bend loss is related to bend radius and conduction laser wavelength. Measure optical fiber was G.652. So parameters are (i) Core radius, a = 14.2 µm, n1 =1.50047, n2=1.5.

    (ii) The core radius, a = 14.3µm, n1 = 1.50047 n2 = 1.5, R =

    100 mm.

    For single mode fiber we change the wavelength and radius the bend of the cable. This table-1 show bends loss of single mode fiber at wavelength 1310nm.

    Table No. 1

    Being based on these parameters, we can draw two charts that showed the dependence of bend loss on both radius and wavelength. Comparing measurements with the theoretical value. We can come to a conclusion that the errors were not large, as in Figure1 showed.

    Fig. 2-comparing the value of the academic and practical on the bend loss.

    Fig3- the bend loss of two wavelength

    Show the bend loss of power meter shined the lasers with the wavelength of 1550nm and 1310nm. There were bending loss measurement dates of them, as Figure 5 showed. As can be seen from the graph, losses at a wavelength of 1550nm were greater than at 1310nm under the same bending radius. Now comparing the bend loss of single mode fiber in different radius with the standard table.

    Table No-2

    Here can be seen in this table error is large compare to table no-1. We can come to conclusion error is not large with increase no. of radius .So, this table use for verify the previous table of measurement of bend loss in different radius.

    Table No-3

    Fig.5- wave form of straight fibe

    In figure ( 5) show curve by OTDR when cable has no bend,

    here can be seen cable goes to straight. In figure (6) cable bend at below 5mm than o/p get to distorted that means if cable bend at below 5mm than o/p power get more losses. In figure ( 7) when cable bend at 11 mm radius than o/p power get less loss .It can be measure by Power meter.

    It proved that loss can be reduced at particular radius with the help of power meter and OTDR .if cable bend at below 5 mm than utput power get more loss. So it has limitation cable can not be bend at below 5 mm.


In this paper a study of bending loss of the fiber cable at diffrerent radius at different wavelength of single and multimode fiber.and reduce the bend loss of both fiber cable at 11mm for single mode and 12 mm for multimode fiber.Show the result calculate the bend loss about single mode and multimode and test proved that the bend loss varied inversely as the bending radius with the wavelength being constant,At the same time ,Some radius of bend cable by power meter ,when having a bend in different positions. So comparing the measured curve that was got in real time with curves.

Fig.6-The loss line in bend radius at 8 mm

Fig 7- The loss line in bend radius at 11 mm


We would like to thanks our honorable teacher a Pawan Kr. Sen. (Assistant Professor) Electrical Department Invertis University Bareilly for his great help and precious suggestions about this work.



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