Practical Application of Fiber Components Manufactured by Bonacom in Fiber-Optic Current Sensor

 

Fiber-optic current sensors are very attractive for the measurement of alternating currents in high-voltage substations as well as of high direct currents (dc), e.g. in the electro-winning industry (electrolytic production of metals such as aluminum, copper, zinc, etc). Benefits compared to conventional devices include enha-

nced performance, wide bandwidth, light weight and small size, high application flexibility and safety of operation. The measurement of short circuit currents in case of faults and high dc in electrolytic processes requires a dynamic range of several orders of magnitude up to about 500 kA. Particularly for high DC the se-

nsors must be very accurate (to within ±0.1 %) over a wide range of temperatures.

 

There are basically two linear effects by which the magnetic field can be measured by optical sensors: magneto-optic effect (or Faraday effect,shown in Fig.11) and magnetic force (or Lorentz force). 

 

Figure 12 shows schematically a current sensing Sagnac interferometer, which is commonly used in gyroscopes and it is sensitive to non-reciprocal effects. This interferometer is interrogated by using a heterodyne detection scheme.

In this particular application, light from an optical broadband source, is linearly polarized with a Bonacom’s in-line fiber polarizer(ILP,BNILP-55-1) and is injected into the Sagnac loop with crossed λ/4-wave plates mounted at an angle of 45° and −45° relative to the plane of polarization of the linearly polarized inputs, for t-

he upper and lower plate, respectively. Some disadvantages of using this type of interferometer include temperature and vibration dependent sensitivities.

 

An improved version of the above system can be done in a reflection configuration, as shown in Figure 13.

Between the optical source and the λ/4-wave plate, the polarized light is injected at 45° into a polarization maintaining fiber (PMF). After crossing the PMF, the λ/4-wave plate which is oriented at 45° with respect to the birefringence axis of the PMF, transforms the two orthogonal polarization modes into circular polariza-

tion modes with opposite rotation directions.

 

Bonacom manufactures various polarization maintaining fiber components for High Power Fiber Optical Current Sensor, e.g.: in-line polarizer(ILP),fiber coupler(filter/fused based-PM/non-PM) with broadband working wavelength at 1310nm,1550nm.

 

We also offer custom optical modules and subsystems by integrating multiple broadband components such as polarization maintaining(PM) isolator coupler FWDM PBS hybrid. These components are ideal choices for developing Fiber Current Sensing systems. Contact Bonacom Technology to discuss your require-

ments.