Showing papers on "Mode scrambler published in 1986"

Highly selective evanescent modal filter for two-mode optical fibers.

Abstract: Efficient and selective coupling between a single-mode fiber and the LP11 mode of a double-mode fiber is demonstrated in an evanescent directional coupler. With greater than 90% coupling to the LP11 mode, suppression of the coupled power to the lower-order LP01 mode was measured to be at least 24 dB. This device has application as a modal filter for the construction of in-line all-fiber optical components.

High power mode conversion for linearly polarized HE11 hybrid mode output

Abstract: Efficient plasma heating by ECR-wave irradiation requires axisymmetric, narrow, pencil-like millimetre wave beams with well-defined polarization. The linearly polarized gaussian-like HE11, mode satisfies these conditions best. This quasi-optical hybrid mode can be generated from TE0n gyrotron mode compositions by the two multi-step mode conversion processes: (1) ΣTE0n to TE01 to TE11 to HE11 or (2) ΣTE0n to TE01 to TM11 to HE11. The first scheme has the advantage that the converters can all be made without bends, allowing an arbitrary choice and fast change of the polarization plane. The second scheme does not exhibit this advantage, but it is more suitable at very high frequencies (e.g. 140GHz) because efficient TE01-to-TM11 transducers can be made considerably shorter than serpentine TE01-to-TE11 mode converters. This paper presents computations on mode converter systems of the first type at 70GHz and of both types at 140GHz (ID = 27 · 8 mm for 200kW transmission lines). The structure of wall perturbati...

Non-reactive radial line power divider/combiner with integral mode filters

Abstract: A parallel plate radial transmission line (14) having parallel plate spacing of less than lambda/2 and which utilizes a specific higher order mode, preferably the first higher order circumferential mode. Undesired modes are suppressed by mode suppression slots (66) formed in one or both of the parallel plates and which are oriented parallel to the current flow lines (68) of the particular mode that is used. These slots (66) have a negligible effect on the mode being used but they couple out other modes that are generated by means such as by imperfections and imbalances in any active devices (36) coupled to the radial line. A centrally located feed is used to launch circularly polarized energy of the TE11 mode in the particular circumferential mode in the radial line (14). The feed may also receive circularly polarized energy of the particular circumferential mode in the radial line, linearly polarize that received energy and conduct it in the TE11 mode.

Single Mode Coupler Manufacturing

Abstract: Until recently, single mode couplers were laboratory curiosities. Now, however, several companies offer high quality couplers as commercial products. Improvements in coupler manufacturing have been made, on a regular basis, to the point where 50% couplers with less than 0.5 dB loss are routinely available. Generally, these couplers are fabricated by hand, a, process which is inefficient, in terms of the consistency of the couplers fabricated and extremely labor intensive, thereby limiting total output. In this paper, we discuss an automated single mode coupler facility. This assembly system has the advantages of high yield, reproducible coupling ratio and loss values, and high volume output.

The influence of mode partition fluctuations in nearly single longitudinal mode lasers

Abstract: A simple relationship between the mode ratio of a two-mode laser and an empirical mode partition coefficient is derived. The effects of the mode ratio of a two-mode laser on the bit-error-rate floor of an optical fiber system are calculated, and the power penalties due to mode partitioning in the presence of Gaussian receiver noise are evaluated. The analysis provides a simple way to calculate the effects of mode ratio on the sensitivity of optical receivers.

A Ball-Bed Mode Mixer For Fiber Evaluation And Micro-Optic Device Assembly

Abstract: A deliberate employment of mode mixing is utilized to make a source that illuminates a fiber in the simulated "steady state distribution". Mode mixing is achieved by combining power exchange due to bending and micro-bending. Discussing these effects design criteria are derived and a practical solution is given. These mode mixers have been used for fiber evaluation and high quality device assembly.

Testing device for mode scrambler

Abstract: PURPOSE:To measure transmission characteristics with good reproducibility by calculating the difference between projection light from a pinhole when the diameter of the pinhole is (r) and that when (r+DELTAr) while rotatig a turntable, and obtaining a far visual field image. CONSTITUTION:The calculation of the far visual field image (FEP) of light projected frm an annular fine part 4 of a graded type optical fiber 1 between the radii (r) and (r+DELTAr) of the core 2 is carried out on the basis of the difference between the projection light when the diameter of the pinhole 6 is (r) and that when (r+DELTAr). Then, this is measured and computed while the turntable 7 is rotated successively to obtain FEP11. Then, such a mode scrambler that FEP11 of the annular fine part with constant width is equal is used. Consequently, the reproducibility of measurements of transmission band width and light loss is obtained.

Characteristics of a single‐mode fiber beyond the cutoff frequency of the LP11 mode

Abstract: To clarify the basis of the concept of effective cutoff wavelength useful for design of single mode optical fibers, this paper discusses theoretically and experimentally the mode conversion effect due to fluctuation of the fiber structure in addition to the difference of the attenuation constants of the modes. In the two-mode region, the scattering matrix elements of the optical fiber are measured with respect to the power of the LP01 and LP11 modes. Based on the measurement, the wavelength dependence of the mode conversion coefficient h and the mode attenuation αi are determined. Next, the multimode dispersion and excess loss of the two-mode system with mode conversion are related to the parameters h and αi and the significance of the effective cutoff wavelength is discussed. It is found that at frequencies slightly beyond the theoretical cutoff for the measured sample fiber the difference of attenuation constants of two modes is substantial. In addition, since the mode conversion coefficient is small, the degradation of the transmission characteristics due to the higher order mode is reduced, resulting in the effective single mode transmission line. Also found is the condition to be satisfied by h and αi so that the desired transmission characteristics (dispersion and loss) are realized with a necessary length of fiber.

Transport of Wideband Data and Video Services over a Single Mode Fiber at 1.3 Micron Wavelength.

Abstract: INTRODUCTION For the last 25 years video has been transported in the broadcast and professional environment using the Serial Digital Interface (SDI) over coaxial cable. The success of this technology has been phenomenal, with data rates up to 3 Gb/s transported for many tens, or even hundreds, of metres over cable that looks no different from that designed for 4.2 MHz of NTSC. But there are always requirements for longer runs, and digital signals over cable have a very well defined quality cutoff point with cable length.

Transmission performance impairment due to degradation of optical spectrum in -1.55 μm DFB laser

Abstract: The dynamic optical spectrum and optical transmission characteristics of a 1.55 μm conventional distributed feedback (DFB) laser with a side mode were analysed. The laser used in the experiment came to operate in two modes although initially it had operated in single-mode. When this laser was directly modulated by setting the bias current around the threshold, the mode switching between a main mode and a side mode was observed to be similar to mode partitioning in Fabry-Perot (FP) lasers. The mode switching affects considerably the bit error rate performance of 113 km single-mode fibre transmission at 140 Mbit/s.

Optical Component Specifications for Fiberoptics

Abstract: Optical Component Specifications for FiberopticsDennis C. LeinerLeiner AssociatesRoute 137, R.F.D. 1, Box 665A, Hancock, New Hampshire 03449AbstractSingle mode optical communication systems place stringent demands on the opto- mechanicaldesign. Tight tolerances on the stability of connector and source coupling efficienciestranslate to unreasonable tolerances on the optical components and mounts. Current designconcepts for fiberoptic interconnection devices are reviewed and their impact on systemspecifications is discussed.IntroductionMultimode optical fiber is usually the preferred transmission medium for all but thehighest bandwidth and longest repeater length fiberoptic communication systems. For largecapacity optical communication, single mode fibers are largely replacing graded -indexmultimode fibers. Lower bandwidth systems can also be fitted with single mode fiber forfuture upgradability. Fiber attenuation losses are currently less than 0.5 dB /km andextremely small dispersion exists in the 1.3 -1.5 micrometer wavelength region. This hasresulted in single mode systems with repeater spacings primarily determined by transmissionlosses in coupling from the optical fiber to the laser diode source and from splicesbetween the optical fibers.Fiber ConnectorsFor permanent splices between single mode fibers, the use of auxiliary optical