Optical Waveguide Theory

Curious wave phenomena that occur in optical fibres due to the interplay of instability and nonlinear effects are reviewed.

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Instabilities, breathers and rogue waves in optics

Graphene plasmons were predicted to possess ultra-strong field confinement and very low damping at the same time, enabling new classes of devices for deep subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. While all of these great prospects require low damping, thus far strong plasmon damping was observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this letter we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine dispersion and particularly plasmon damping in real space. We find unprecedented low plasmon damping combined with strong field confinement, and identify the main damping channels as intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key for the development of graphene nano-photonic and nano-optoelectronic devices.

Highly confined low-loss plasmons in graphene-boron nitride heterostructures

Space-division multiplexing (SDM) uses multiplicity of space channels to increase capacity for optical communication. It is applicable for optical communication in both free space and guided waves. This paper focuses on SDM for fiber-optic communication using few-mode fibers or multimode fibers, in particular on the critical challenge of mode crosstalk. Multiple-input–multiple-output (MIMO) equalization methods developed for wireless communication can be applied as an electronic method to equalize mode crosstalk. Optical approaches, including differential modal group delay management, strong mode coupling, and multicore fibers, are necessary to bring the computational complexity for MIMO mode crosstalk equalization to practical levels. Progress in passive devices, such as (de)multiplexers, and active devices, such as amplifiers and switches, which are considered straightforward challenges in comparison with mode crosstalk, are reviewed. Finally, we present the prospects for SDM in optical transmission and networking.

Space-division multiplexing: the next frontier in optical communication

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross-sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back-reflection. The mode resonances have a quality factor of 105, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).

Tilted fiber Bragg grating sensors

The arbitrary quadruple-step-index structure is examined as a new design model for dispersion-flattened fibers to obtain more degrees of freedom and simulate the practical fiber profile. The effects and limitations of structural factors are examined. Under the severe condition of the first clad depression - Delta n/sub 1/ >

Attenuation-optimized dispersion-flattened quadruple-clad fibers with moderate F-doping in the first inner cladding

In this letter, a novel all-fiber ring laser refractive index (RI) sensor is proposed and experimentally demonstrated. Such sensor is obtained by inserting a segment of cladding-less fiber between two sections of single-mode fiber with one core-offset joint, which is designed to enlarge the extinction ratio. With the help of ring laser sensing system, a 3-dB bandwidth below 0.2 nm and an optical signal-to-noise ratio near 30 dB can be achieved. Meanwhile, the high output power and the side-mode suppression ratio of the sensor are presented. Experimental results show that the RI sensitivity is 52.3 nm/RIU in the RI range of 1.334–1.370. The sensor also has the advantages of simple structure and low cost, preforming potentials in large-scale productions.

RI Ring Laser Sensor Based on Concatenating CLF and SMF With One Core-Offset Joint

A numerical analysis of GeO 2 -doped multi-step index single-mode fiber for stimulated Brillouin scattering

The mode-spacing of the fiber Bragg grating Fabry-Perot (FBG F-P) cavity is calculated by using the effective cavity length which contains the effective length of the FBG. The expression of the effective length, defined by using the phase-time delay, is obtained and simplified as a function of the peak reflectivity at the Bragg wavelength, the band edges, and the first zero-reffectivity wavelength. The effective length is discussed from the energy penetration depth point of view. Three FBG F-P cavities are fabricated in order to validate the effective length approach. The experimental data fits well with the theoretical predictions. The limitation of this method is also pointed out and the improved approach is proposed.

Theoretical and experimental investigation of the mode-spacing of fiber Bragg grating Fabry-Perot cavity

We propose a novel method to analyze Raman amplifiers (RAs) by solving difference equations. This method is highly convenient for analysis of the transient effects of Raman amplifiers under dynamic conditions. Some properties of time-division multiplexing (TDM)-pumped RAs are analyzed theoretically. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 407–410, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20154

Shuisheng Jian

Papers

Attenuation-optimized dispersion-flattened quadruple-clad fibers with moderate F-doping in the first inner cladding

RI Ring Laser Sensor Based on Concatenating CLF and SMF With One Core-Offset Joint

A numerical analysis of GeO 2 -doped multi-step index single-mode fiber for stimulated Brillouin scattering

Theoretical and experimental investigation of the mode-spacing of fiber Bragg grating Fabry-Perot cavity

Analysis of Raman amplifiers' transient effects and TDM-pumped Raman amplifiers using the finite-difference method