Showing papers on "Mode scrambler published in 2003"

Quantitative estimates of mode coupling and differential modal attenuation in perfluorinated graded-index plastic optical fiber

Abstract: The performance of plastic optical fiber is greatly influenced by the related but distinct effects of mode coupling and differential modal attenuation (DMA). We establish a method for estimating the matrix that governs both of these effects and allows us to distinguish the two. We obtain partial quantitative estimates of this matrix for a particular graded-index plastic optical fiber (GI-POF). The sample we studied exhibited strong but incomplete mode coupling over 100-m lengths, while DMA was largely limited to a centerline defect. We show that much of the loss of the fiber can be attributed to mode coupling between mode groups with similar effective indexes.

Quantitative characterization of higher-order mode converters in weakly multimoded fibers.

Abstract: We present a rigorous analysis methodology of fundamental to higher order mode converters in step index few mode optical fibers. We demonstrate experimental conversion from a fundamental LP01 mode to the higher order LP11 mode utilizing a multiple mechanical bend mode converter.We perform a quantitative analysis of the measured light intensity, and demonstrate a modal decomposition algorithm to characterize the modal content excited in the fiber. Theoretical modelling of the current mode converter is then performed and compared with experimental findings.

Electrical spectrum measurements of dispersion in higher order mode fibers

Abstract: We present a novel technique for measuring the chromatic dispersion of the higher order mode of an optical fiber. The measurement technique is simple, accurate, and capable of measuring the dispersion of kilometer lengths of fiber without the need for mode converters. The dispersion of the LP/sub 02/ mode is measured for several different fibers, and accuracies of better than 1%, compared with a measurement with the modulation phase shift method, are achieved.

Broad-band LP 02 mode excitation using a fused-type mode-selective coupler

Abstract: We demonstrate a novel fused-type directional coupler that couples the LP/sub 01/ mode in one fiber and the LP/sub 02/ mode in another using a few-mode fiber. The phase-matching condition was satisfied in the coupler waist by initially etching and prepulling portions of the fibers based on simple numerical calculation. A coupling efficiency of about 70% was maintained over 1515-1595-nm wavelength range, and the mode extinction ratios with LP/sub 01/, LP,/sub 11/, and LP/sub 21/ modes were measured to be 35,20, and 7 dB, respectively.

Off-axis mode scrambler

Abstract: An apparatus and method for generating a mode-scrambled optical signal (10). A laser beam (12) directs an optical signal (14) into a free end (22) of a first segment of multimode fiber comprising a graded-index (GI) fiber core (16) at an offset from the centerline of the core, generating an offset-launch condition. The first segment of multimode fiber is operatively coupled into a second segment of multimode fiber comprising a step-index (SI) fiber core (18). As the offset-launched optical signal passes through the first and second segments of multimode fiber, the optical signal is converted into a mode-scrambled optical signal (24) having a substantially-filled numerical aperture.

Method and apparatus for optical mode division multiplexing and demultiplexing

Abstract: A method of mode selective coupling or mode multiplexing between integrated multimode (600) and single mode (602) waveguides. Evanescent coupling and tapering is used so that the signal may be transferred adiabatically from a first region of a first waveguide to a second, proximal, region of a second waveguide.

Multi-mode amplification system

Abstract: PROBLEM TO BE SOLVED: To provide a multi-mode amplification system the operating mode of which can be switched for a linear mode, an envelope tracking mode, and a polar mode. SOLUTION: A mode selector 16 controls the mode of an amplifier 22 so as to be operative in the linear mode when the level of an input signal is lower than two threshold levels T L1 , T L2 , in the polar mode when the level of the input signal is higher, and in the envelope tracking mode when the level of the input signal is intermediate. For the purpose of mode selection, the mode selector 16 supplies an amplitude modulated signal plus a variable headroom voltage to a power supply terminal of the amplifier 22 in the envelope tracking mode, supplies the amplitude modulated signal and the phase modulated input signal to the power supply terminal in the polar mode, and supplies a signal with a prescribed amplitude to the power supply terminal in the linear mode. COPYRIGHT: (C)2005,JPO&NCIPI

High-capacity multimode optical fiber systems

Abstract: Multimode optical fiber local area networks, both intrabuilding and interbuilding, are optimized to take advantage of the wide wavelength operating range offered by co-pending patent application Ser. No. 10/408,076 “Enhanced Multimode Fiber” —a fiber provided both with: longitudinally spaced perturbations for inducing mode coupling and thereby lessening mode dispersion; and with a radial discontinuity for discouraging conversion of bound-to-cladding-modes and thereby lessening added loss previously associated with induced mode coupling.

Optical mode converter

Abstract: An optical mode converter comprising an optical guide able to transmit an optical signal in at least one guided mode, characterised in that the optical guide comprises a photosensitive zone inducing a specific index profile along a section of the guide, the said index profile simultaneously defining a longitudinal adiabatic transition and a transverse distribution of the guided mode or modes so as to deconfine the fundamental mode and to maximise the overlap with a higher-order mode.

Optical tunable microwave filter using higher mode

Abstract: Disclosed is an optical tunable microwave filter using higher mode. The filter comprises a laser diode producing carrier signals; a modulator modulating the signals produced by the laser diode; a first mode converter being input power of the modulated signals by the modulator and dispersing the power of the input signals, namely the power of the signal with a mode (LP01) in a single mode fiber, into two modes (LP01, LP02) in a dispersion compensation fiber; a second mode converter being input two modes (LP01, LP02) signals having time delay through the first mode converter and converting the input modes (LP01, LP02) signals into a mode (LP01) existing in the single mode fiber; a receiver receiving the signals converted by the second mode converter.

Development of an Adaptive Polarization-Mode Dispersion Compensation System

Abstract: Polarization-mode dispersion (PMD), in single-mode optical fibers, is a phenomenon that can limit the bit-rate-distance product of amplified, lightwave communication systems. PMD compensation is a solution to overcome the limitations posed by PMD. However, compensation is complicated due to the random nature of PMD. Therefore, adaptive compensation techniques are required. We modified an adaptive PMD compensation system that was earlier developed and made it robust and bit-rate independent. The new setup uses the degree of polarization (DOP) of the received optical signal for monitoring the fiber-link's PMD. An analog voltage equivalent of the DOP, commonly referred to as the PMD monitor signal, is used for the PMD compensation. We performed experiments to identify the effect of polarization scrambling on the PMD monitor signal and to find the appropriate range of scrambling frequencies. The appropriate polarization scrambling frequency range for the present setup was determined to be between 80 Hz and 100 Hz. Next, we performed different tests on the adaptive PMD compensation system. The time taken by the compensator to complete a compensation cycle was determined to be 100 s. OSNR (optical signal to noise ratio) tests were conducted from which it was determined that the PMD compensator could perform satisfactory compensation at 10 dB of OSNR and above. We then successfully performed a field trial of the adaptive PMD compensation system on an underground fiber-optic link spanning about 95 km.

Characteristics of the transmission spectrum of the long period fiber gratings based on the coupling of core mode to the higher order cladding modes

Abstract: The characteristics of the transmission spectrum of the Long-period fiber gratings (LPFGs) based on the coupling of core mode to a higher order cladding mode (HE mode) are investigated using the coupled mode theory. This kind of LPFGs is different from that based on the coupling of core mode to a lower order cladding mode because of the effect of the coupling of core mode to EH cladding mode. When the cladding mode order is higher, the coupling coefficients of core mode to HE and EH cladding modes are comparable and both of the propagation constants of HE and EH cladding modes approach, so the spectrum has an additional loss peak. The bandwidth of LPFG based on the coupling of core mode to different cladding mode differs greatly. With the change of the mode orders from lower to higher, the transmission spectrum changes from narrow to wide and more narrow.

Fiber-optic interferometer and interfering method thereof

Abstract: A fiber-optic interferometer is provided. The interferometer includes a first dual-mode optical fiber for receiving a light input and exciting a first spatial mode and a second spatial mode, a first modal processor connected to the first dual-mode optical fiber for selecting the first spatial mode and the second spatial mode, a second dual-mode optical fiber connected to the first modal processor for propagating the first spatial mode and the second spatial mode and producing a phase shift (Δ φ) between the first spatial mode and the second spatial mode in response to an external perturbation effect, a second modal processor connected to the second dual-mode optical fiber for re-selecting the first spatial mode and the second spatial mode and producing a first light output interference pattern, and an analyzer having a polarization axis and connected to the second modal filter for adjusting the first light output interference pattern to produce a second light output interference pattern, so that the second light output interference pattern obtains an optimal contrast (C) through an adjustment of the polarization axis.

Measurement of second-order polarization mode dispersion in single mode fiber with Poincare sphere method

Abstract: We measured the second-order polarization mode dispersion (SOPMD) in a 75 km single mode fiber with the Poincare sphere method. The parallel component and perpendicular component (also called the depolarization component) of SOPMD were analyzed, and the statistical properties of them were also analyzed. According to these we found that the perpendicular component has a greater impact on pulse than that of the parallel component in mean.

Mode filtering and mode selection for multimode optical fibre with core and envelope, which has periodic index structure with rising reflection capacity of envelope only for specified transversal mode

Abstract: The multimode optical fibre has core and envelope, with latter containing periodic index structure, with increasing reflection capacity of envelope for specified transversal mode only. Thus only this transversal mode can propagate along optical fibre. For mode selection optical fibre cross-section has periodically variable refraction index structure, which permits only specified mode to propagate along optical fibre, with specified mode selected as desired mode only. An Independent claim is also included for optical fibre.

Concept of a quasi-optic power amplifier utilising a new converter of mode TE10 to TE20

Abstract: A new converter of mode TE10 to TE20 was developed for application in spatial power controller in a rectangular waveguide with slot profile (Finline).lt permits conversion of a TE10 mode to TE20 mode, eliminating the TE10 mode. One concept in Ku band (14-14.5 GHz) was successfully tested. The converter allows a TE20 mode to be obtained with suppression of the TE10 mode at less than 22 dB. This converter was employed for a 2 W power amplifier with an efficiency of 85%. A new measurement technique was developed for measuring the electric field profile in the interior of the rectangular waveguide.

Second harmonic generation with a high-order mode laser beam

Abstract: Second harmonic generation can be highly efficient with a laser operating with a single high order mode. A 90% increase in output power was obtained with a Q-Switch Nd:YAG laser when it was operating with TEM01 rather than TEM00 mode.