Understanding Optical Fiber Polarization Mode Dispersion

While they travel along with fiber, Dispersion with polarization maintaining splitter is the fact that light pulses spread out. Because the speed of light in the fiber depends on the propagation mode and its wavelength i.e. the light color, this fact occurs.

A small range of wavelengths (colors) constitutes the light pulses in optical fibers. Practically, a pure single colored light can be generated by no light source. In either a relatively broad range as a LED or a narrow wavelength range as a semiconductor laser, they generate light always.

Various light wavelengths travel at different speeds in optical fibers. This means as compared to others, at the receiver, some might arrive a bit later. As compared to that of the transmitter side, this fact offers broader received light pulses. Dispersion is this pulse broadening.

By the dependence of refractive index on wavelength, the transmission of two different polarizations of light (PMD), multimode transmission (different mode travels at a different speed), and variations in waveguide (optical fiber) properties with wavelength, Dispersion with polarization maintaining isolator can also be caused through single-mode fibers. In a fiber-optic digital communication system, Dispersion's impact on bit rate is present.

Dispersion can limit the distance a lightwave signal can travel through an optical fiber like power loss in a fiber optic link. But it makes the signal blurry; dispersion does not weaken a signal different than attenuation. For example, at the end of the fiber, the pulse spreads to 10 milliseconds if you send out a 1-millisecond width pulse but then in time that the signal becomes unintelligible, signals blur together.

Impact of PMD on single-mode fiber optic systems

Only a few years ago, Getting significant when high-speed fiber-optic digital communication systems came to play, such as the 40Gbit/s systems, the potential effects of polarization mode dispersion occurs. In magnitude, Polarization mode dispersion (PMD) with polarization maintaining circulator is smaller than other types of dispersions, but at least until now, it is tougher to compensate for. With data rates higher than 2.5Gbit/s, PMD becomes a problem in systems. To sending higher data rates, PMD makes more challenges over long distances.