Design considerations of depressed clad W-shaped single mode dispersion compensating fibers

Dispersion compensating fibers (DCFs) are being widely used as dispersion compensation techniques because of its superior characteristics. This work reports the theoretical modelling of a single mode DCF having W-shaped shallow as well as deeply depressed clad profile. The DCFs have been designed and optimized by suitable adjusting different fiber parameters such as, central relative index difference (Δ⁺), inner core radius (a), depression depth parameter (ρ), normalized end position of the depressed clad (p), etc. at a given spot size . The figure of merit (FOM) characteristics including the bend loss as well as other losses associated with fiber manufacturing technique have been thoroughly investigated. Performances of these DCFs for recent wavelength division multiplexing (WDM) transmission system have also been discussed. By adjusting different fiber parameters, the effective core area (A_eff) of the above DCFs can be controlled to minimize the effect of non-linearities on them.     

Selection of mandrel wrap mode filters for optical fiber loss measurements

A selection criterion for mode filters based on far-field patterns is developed. The criterion is used to select a mandrel wrap filter for 50 μm core diameter, 125 μm outside diameter fibers with δ=1.1%. When cut-back loss measurements were made using the mandrel wrap chosen in this way, loss scaled with length to within ± 0.05 dB/km in three 2-km fibers.     

Highly birefrigent photonic crystal fiber with high negative dispersion for broadband dispersion compensation

In this paper, we proposed a dual-enhanced core photonic crystal fiber (PCF) with high birefringence and ultra-high negative dispersion for dispersion compensation in a polarization maintained optical system. Using finite difference time domain (FDTD) method, we presented dispersion compensating PCF (DC-PCF) with negative dispersion between −1650 ps nm⁻¹ km⁻¹ and −2305 ps nm⁻¹ km⁻¹ in C-band and particularly −2108 ps nm⁻¹ km⁻¹ in λ = 1.55 μm wavelength. By this method, we can compensate dispersion in 124 km long span of a conventional single mode fiber (SMF) by 1 km-long of the DC-PCF at λ = 1.55 μm wavelength. Moreover, fundamental mode of the proposed PCF can induce birefringence about 3.5 × 10⁻³ at 1.55 μm wavelength.     

Modeling of a step index segmented core single mode optical fiber as a dispersion compensator

A segmented core central step index dispersion compensating fiber (DCF) has been modeled by using spot size optimization technique. We have designed and optimized the DCF by suitably adjusting different fiber parameters, i.e. inner core radius (a), central relative refractive index difference (Δ), normalized outer core position (p), width (b) and height (h) at different values of given Petermann-II spot sizes . The studies on the propagation behavior as well as bendloss and other losses of the DCF have been presented here. The proposed design of the DCF can possess improved bend performances over single core DCFs. At the same time higher negative dispersion coefficient in the single mode region as well as considerably high value of figure of merit (FOM) for optimized fiber parameters can be achieved for smaller spot sizes of the DCF. Further, inclusion of length independent splice loss modified this conventional FOM to a slightly lesser value of modified FOM.     

Dispersion-Compensating Graded Index Multiclad Fiber: Optimization for Dispersion-Managed WDM Transmission Systems

This work reports the design optimization of a single-mode graded index multiclad dispersion-compensating fiber (DCF) with a central dip, for broadband wavelength division multiplexing (WDM) system in the C- and L-bands of an operating wavelength zone. The index profile parameters of this fiber have been adjusted to simultaneously achieve high figure of merit (FOM) as well as considerably high value of effective core areas of the fiber to minimize the nonlinear effects like self-phase modulation or cross-phase modulation. At 1,550 nm operating wavelength, an effective core area (A_eff) of 46 μm², which is very large compared to other reported values of DCFs, is obtained here. The average dispersion of the DCFs, in combination with conventional single-mode fiber (CSF) and small dispersion fiber (SDF), are found out to be considerably flat in the entire C- and L-band zone of operating wavelength.     

Experimental realization of a novel dispersion- compensating optical fiber amplifier for simultaneous compensation of positive dispersion and losses

Erbium-doped dispersion-compensating optical fiber (EDCF) has been theoretically simulated and experimentally fabricated using Modified Chemical Vapor Deposition (MCVD) for optimum operation at 5.0km. It is optimized for both gain as well as negative dispersion. The erbium has been doped into the cladding region while the core of the optical fiber is chosen to be narrow so as to have a high negative dispersion. Measured gain of 3.1 dB at 200 m using 100 mW pumping power (980 nm wavelength) at 1550 nm has been obtained and the gain of 32 dB at 5.0 km using same pumping scheme has been predicted. The chromatic dispersion of this EDCF has been also measured to be –43.5 ps/km-nm at 1550 nm and thus, providing the dispersion of –217.5 ps/nm at 5 km. The bend-induced losses are found to be negligible. We are the first to report the experimental realization of EDCF.