Optical fiber-based dispersion compensation using higher order modes near cutoff

An Overview of Array Signal Processing and Beam Forming Techniques

“…The physical relationship describing acoustic waves is similar to that of light λ f = c. The frequencies of signals that an array detects are important because they determine constraints on the spacing of the sensors. The array's sensors sample incident signal in space and, just as aliasing occur in analog to digital conversion when the sampling rate does not meet the Nyquist criterion, aliasing can also happen in space if the sensors are not sufficiently close together [3]. A useful property of the uniform linear array is that the delay from one sensor to the next is uniform across the array because of their equidistant spacing.…”

Fiber-modes and fiber-anisotropy characterization using low-coherence interferometry

“…Figure 1 shows the first few modes of a circular step-index fiber [1]. The true vectorial eigenmodes are displayed in the first row.…”

“…For example, it is well known that in a multimode optical fiber the transverse modes possess different characteristic group velocities. The knowledge of the intermodal dispersion characteristics of multimode fibers is of interest for the design of optical transmission systems, as well as for other applications such as dispersion compensation [1], fiber refractive-index profile characterization [2], and a variety of in-fiber devices [3]. In this context it is necessary to identify the individual transverse modes [2,4] to precisely characterize the dispersion properties.…”

Dispersion Compensation in Optical Communication Link Using Apf’s

“…After the various channels have been multiplexed by the wavelength interleaver over the single fiber the next step is to compensate the phase distortions due to different group delays for different channels [1], [7]. Dispersion compensating fibers [2], [3] (with opposite chromatic dispersion as that of channels) are not used these days as they introduce large footprint, high insertion loss, introduce nonlinear distortion etc, hence they have been replaced by all pass filter structure. It is a special filter with flat magnitude spectrum and non-linear phase spectrum, so it compensates phase distortion without affecting magnitude spectrum of signals [8], [9].…”

“…Since the energy levels are not discrete so mono-chromaticity of the light signal is lost and it introduces chromatic dispersion. The number of compensating techniques has been reported in the literature [3], [4], [5], [6] including dispersion compensating fibers (DCFs), Fiber Bragg gratings (FBGs), Electronic Dispersion compensation (EDC) each having its own advantages and disadvantages. In WDM system where a number of frequencies are interleaved, dispersion is compensated using all pass filters [7].…”