W-type Fiber Research Articles

Single mode graded-core W-type fibers with low dispersion over a wide spectral range

We have studied the validity of the scalar approximation to evaluate chromatic dispersion in single-mode W-type fibers. Based on this approximation we compute the design parameters of a single-mode graded-core W-type fiber which will have very low dispersion over a wide spectral range. The advantages of graded-core W-type fibers over homogeneous core fibers are discussed.

Some characteristics of the polarization properties of single-modeW-type waveguides

An experimental investigation was made of the natural birefringence and of the spectral dependence of the maximum degree of polarization of light traveling in three-layer single-mode W-type fiber waveguides. The linear and circular birefringence was determined. An analysis of the spectral dependence of the maximum degree of polarization revealed a coupling between the dominant and leaky modes in the investigated fiber waveguide. The results obtained were used to estimate the coupling coefficient.

Design Consideration on Broad-Band W-Type Two-Mode Optical Fibers

Structural design for broad-band W-type two-mode optical fibers is investigated. The optimum parameters are numerically determined as follows: the operating V-value with zero group delay time difference Delta lambda between the LP/sub 01/ and LP/sub 11/ modes is 6.7, the ratio of core radius to inner cladding radius is 0.6, and the index profile parameter is 2.02. then, the core radius is 12.3 µm for Delta=0.3 percent at the operating wavelength of 1.3 µm. The V-value deviation tolerance from the optimum to maintain Delta lambda less than +-20 ps/km is 21 percent, which is 20 times larger than that of the earlier design made on two-layer index profile.

Analytical approximation for W-type fibre propagation parameters

We present an analytical formula giving a good approximation of propagation and dispersion parameters for W-type fibres, together with a physical explanation of their remarkable dispersion properties.

Single-mode low-lossW-type fiber waveguide

A single-mode W-type fiber waveguide was made and investigated experimentally for the first time. The higher-mode cutoff wavelength was 1.04 μ when the core diameter was 13.5 μ. The minimum losses were 3.2 dB/km in the 1.2 μ range. This waveguide should be very useful for data transmission in long-distance wideband communication lines.

Experimental study of single-mode W-type optical fibre

The development and experimental study of a single-mode W-type optical fibre is described. It was found that this type of optical fibre has considerably lower bending and micro-bending losses compared with usual single-mode single-cladding fibres.

Erratum: Cutoff frequencies of W-type fibre with polynomial profile core

Erratum: Cutoff frequencies of W-type fibre with polynomial profile core

Cutoff frequencies of W-type fibre with polynomial profile core

Cutoff frequencies of the guided modes in a graded-index fibre with a finitely thick cladding are calculated by a refined WKB method. The results are in good agreement with the exact ones for the parabolic core fibre. The effect of the fourth order correction to the parabolic core fibre on the cutoff frequency is evaluated.

Numerical solution of power flow in multimode W-type optical fibers

Transmission characteristics of multimode step-index W-type optical fibers are theoretically investigated by numerically solving the complex power flow equations. Spatial transients of power distribution and power level, as well as transmission length dependence of transmission bandwidth, are calculated for the mode-coupling condition from guided to lossy leaky modes, a characteristic of W-type fibers. The transmission characteristics of W-type fibers change from those of two singly clad reference fibers when the width of the intermediate layer is changed. The trade-off relation between the bandwidth and steady-state loss is also discussed.

Steady-state characteristics of multimode W-type fibers

The steady-state characteristics of multimode W-type fibers are investigated by solving the coupled-power equation numerically. It is shown that the steady-state power distributions depend on both the intermediate layer width and the coupling strength. Unlike singly clad fibers, the steady-state loss (coupling-induced loss) in W-type fibers is not proportional to the coupling strength. The loss in W-type fibers varies between the value for two types of singly clad reference fibers as the coupling strength changes.

Graded Core W-type Fibre and Its Propagation Characteristics

Graded Core W-type Fibre and Its Propagation Characteristics

Periodic bending loss in multimode W-type fiber

Additional loss in a W-type fiber induced by periodic bends is investigated experimentally in comparison with the corresponding singly clad (SC p and SC q) fibers. When the bending amplitude is small, the additional loss of the W-type fiber is almost equal to that of SC p fiber. However, as the amplitude becomes larger, the loss increases and gradually approaches the value for SC q fiber.

Efficient coupling of incoherent light into optical fibers and bundles: errata

The excitation efficiencies of a few lower order modes in a W-type fiber have been studied when the modes are excited with tilted as well as off-set Gaussian beams. The effect of beam size, angle of incidence, the radius of curvature of the incident wavefront, and the off-axis displacement on the excitation efficiencies has been obtained. It is found that in order to couple maximum power into the fundamental mode, the incident wavefront must be plane and the beam must be incident axially along the fiber with a suitable value of the beam size.

Transmission characteristics of multimode W-type optical fiber: experimental study of the effect of the intermediate layer

The transmission mechanism of a multimode W-type optical fiber is clarified by the experimental study of the effect of the intermediate layer on the transmission characteristics. It is shown that control of the layer width is an effective means for achieving the desired loss and bandwidth. A W-type fiber with a thick intermediate layer has a transmission loss on the order of 2 dB/km. To determine the transmission characteristics of a W-type fiber applicable to system design, the length dependence of several fiber characteristics is investigated. Concepts such as splices used as mode scramblers and the effect of the intermediate layer as a barrier against OH absorption loss are introduced. The wavelength dependence of microbending loss of a W-type fiber is also described.

Mode excitation by tilted and offset Gaussian beams in W-type fibers

The excitation efficiencies of a few lower order modes in a W-type fiber have been studied when the modes are excited with a tilted as well as offset Gaussian beams. The effect of beam size, angle of incidence, the radius of curvature of the incident wavefront, and the off-axis displacement has been obtained. It is found that in order to couple maximum power into the fundamental mode, the incident wavefront must be plane, and the beam must be incident axially along the fiber with a suitable value of the beam size.

Efficient coupling of incoherent light into optical fibers and bundles

The excitation efficiencies of a few lower order modes in a W-type fiber have been studied when the modes are excited with tilted as well as off-set Gaussian beams. The effect of beam size, angle of incidence, the radius of curvature of the incident wavefront, and the off-axis displacement on the excitation efficiencies has been obtained. It is found that in order to couple maximum power into the fundamental mode, the incident wavefront must be plane and the beam must be incident axially along the fiber with a suitable value of the beam size.

Cutoff frequencies of a parabolic-core W-type fibre

The cutoff frequencies of guided modes in a weakly guiding W-type fibre with parabolic core profile have been obtained. It is found that the cutoff frequency of the TE01-mode in such a fibre is much higher than for a homogeneous-core W-type fibre. This should allow greater ease in splicing.

Microbending losses of doubly clad (W-type) optical fibers

The microbending of optical fibers causes some additional transmission losses. In this paper, the theoretical and experimental results on the microbending characteristics for doubly clad (W-type) fibers are described. A simple approximation in which W-type fibers are considered as equivalent singly clad fibers is employed to calculate the additional losses due to microbending. It is shown that the additional losses of W-type fibers depend on the optical wavelength. Further, it is shown that the structural imperfections of the guide can be also considered a kind of microbending which affects the spectral loss characteristics of W-type fibers.

W-type optical fiber: relation between refractive index difference and transmission bandwidth

W-type optical fiber: relation between refractive index difference and transmission bandwidth

Special issue paper. Transmission characteristics of W-type optical fibres

Properties of doubly-clad optical fibres with a low-index inner cladding (W-type fibres) as single-mode or multimode transmission lines are discussed both from theoretical and experimental viewpoints. Such fibres are characterised by the tight confinement of the modal power in the core. A small bending loss is one of its consequences. A single-mode W-type fibre can be used at a v-value significantly larger than 2.405, and it has an anomalous dispersion effect. A multimode W-type fibre is also discussed.