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Showing papers on "Mode scrambler published in 1978"


Patent
Love Walter Francis1
17 Nov 1978
TL;DR: In this article, an optical waveguide mode scrambler including a length of high-alpha OO waveguide optically coupled to a low-alpha waveguide which provides efficient spatial and angular mixing of light propagating therethrough is described.
Abstract: An optical waveguide mode scrambler including a length of high-alpha optical waveguide optically coupled to a length of low-alpha optical waveguide which provides efficient spatial and angular mixing of light propagating therethrough is described

49 citations


Journal ArticleDOI
TL;DR: It is shown that a mode coupling coefficient can be calculated from each mode group pulse waveform, and in the fiber sheathed by nylon, there existed a strong mode coupling in lower order modes.
Abstract: The measuring method of the mode coupling coefficient was developed to apply to multimode fibers. It is shown that a mode coupling coefficient can be calculated from each mode group pulse waveform. Measurements were made with two cases of long-length and short-length multimode step-index fibers. As a result, it was observed that in the fiber sheathed by nylon, there existed a strong mode coupling in lower order modes. When it is assumed that this mode coupling is generated by microbendings, the correlation length and standard deviation of the curvature were estimated as 2.0 mm and 4.2 × 10−4 mm−1, respectively.

18 citations


Journal ArticleDOI
TL;DR: A new method for the simultaneous measurement of the loss and mode conversion coefficient in multimode fibers is proposed, which utilizes the differences of the mean transit time among modes.
Abstract: A new method for the simultaneous measurement of the loss and mode conversion coefficient in multimode fibers is proposed, which utilizes the differences of the mean transit time among modes. The principle is applied to a step-index fiber, and the mode conversion coefficient and mode dependent loss are obtained. A procedure to minimize the experimental errors is also discussed. In the experiment the mode conversion coefficient decreases gradually when the mode angle increases and increases rather quickly when the angle approaches the critical angle of the fiber.

12 citations


Patent
21 Nov 1978
TL;DR: In this paper, a mode mixer and a mode stripper are connected in series with the lightwave guide to measure the attenuation of a very long fiber, which corresponds with the "steady state".
Abstract: In order to be able to measure the attenuation of a lightwave guide fiber definitely and reproducibly, it is suggested to offer a mode distribution to the lightwave guide to be measured which corresponds with the "steady state" of a very long fiber. A mode mixer and a mode stripper is for this purpose connected in series with the lightwave guide to be measured. All core modes and leakage- and jacket modes are excited in the mode mixer. In the mode stripper the jacket- and leakage modes are again stripped (absorbed) so that a mode distribution, comparable to the "steady state", remains.

12 citations


Journal ArticleDOI
TL;DR: In this article, a means applicable to any coupling mechanism for treating the effects of mode coupling is given together with formal solutions, which is useful to develop general means to analyze power flow equations.
Abstract: Mode coupling, caused by random variations of core index or random irregularities of the fiber wall, influences the transmission characteristics of multimode optical fibers in a complicated way. The effects of mode coupling in multimode optical fibers have been reported using coupled power equations or power flow equations, and the good agreement between theoretical and experimental results provides further evidence that the power flow equation is a useful description of the power distribution in a multimode optical fiber. From these situations, it would be useful to develop general means to analyze power flow equations. In this paper, a means applicable to any coupling mechanism for treating the effects of mode coupling is given together with formal solutions.

10 citations


Patent
25 Aug 1978
TL;DR: In this paper, the authors proposed to realize the optical communication line of a wide transmission band width substantially equal to that of a single mode fiber by using the mode filter of the simple construction.
Abstract: PURPOSE:To realize the optical communication line of a wide transmission band width substantially equal to that of a single mode fiber by using the mode filter of the simple construction. CONSTITUTION:When the value of the standardized frequency V of a linear multimode optical fiber is larger than 2.4, the effect of confinement of the basic mode into the core is large and the intensity of the basic mode at the boundary of the core and clad becomes weak. Hence, it becomes difficult to receive the effect of disturbances at the boundary of the core and clad and the losses become smaller as against various bendings occuring in cabling and laying. Hence, the single mode is substantially made possible by adding a mode filter 4 function near the receiving end of an optical fiber 5.

8 citations


Journal ArticleDOI
TL;DR: It was observed that mode mixing effects became more noticeable as the mode coupling coefficients increased, and it was found that the excess loss caused by microbends was relatively small.
Abstract: Mode coupling coefficients were measured in a multimode step-index fiber at different steps of the process of manufacturing a multistrand optical fiber cable. It was established that the mode coupling coefficients of the unsheathed fiber were relatively small and nearly the same for all the guided modes. By sheathing with nylon and by multistranding, the mode coupling coefficients between lower-order modes increased rapidly due to microbends, while in the vicinity of the highest-order mode, they remained unchanged. From impulse response waveforms and baseband frequency responses, it was observed that mode mixing effects became more noticeable as the mode coupling coefficients increased. Also, it was found that the excess loss caused by microbends was relatively small.

7 citations


Journal ArticleDOI
TL;DR: It has been found that the transmission bandwidth can be widened by using mode scramblers and the total transfer function calculated by the linear combination of each fiber's transfer function is in good agreement with the measurement results.
Abstract: Transfer functions of long spliced graded-index fibers are described. The transfer function of a spliced graded-index fiber is determined with the steady state mode exciter and the mode scramblers loaded just after each splicing. Under these conditions, the total transfer function calculated by the linear combination of each fiber's transfer function is in good agreement with the measurement results. It has been found that the transmission bandwidth can be widened by using mode scramblers.

4 citations


Journal ArticleDOI
TL;DR: In this paper, the behavior of a fiber laser-amplifier is considered, including the effects of mode coupling, radiation losses, and noise, and a competitive effect between mode coupling and losses is present.
Abstract: The behavior of a fiber laser-amplifier is considered, including the effects of mode coupling, radiation losses, and noise. In the linear regime, a competitive effect between mode coupling and losses is present, in the sense that mode coupling tends to equalize the gains of different modes, while radiation losses favor low-order modes. Thus, single-mode amplification and collective amplification are predominant, respectively, in the weak and strong coupling case. In the saturated regime a mode coupling effect is found that is independent of fiber imperfections and relies on the nonlinear nature of the process.

2 citations