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

Bragg fibres have many special characteristics. Therefore this kind of fibre attracts more and more attention. In this paper, genetic algorithm is applied to design Bragg fibres to realise desired dipersion and attenuation characteristics.

The design of Bragg fibers using genetic algorithm

In this paper we introduce some methods to improve performance of cladding pumped L-band EDFA. C-band seeds, ASE end-reflectors, and hybrid configurations use the cladding pumped fiber and convential EDF have been studied.

Improvement in performance of L-band cladding pumped fiber amplifiers

Time independent rate equations for fiber laser are solved accurately with numerical method under multipoint boundary conditions. A novel method based on genetic algorithm is firstly proposed to optimize distributed pump powers and fiber segment lengths of kilowatt YDDC fiber laser. The uniformity of temperature distribution is improved by using optimized method. The calculated results show that the lower operating temperature and better uniformity can be obtained through increasing the number of segments at the cost of decreased output signal power.

Novel method to optimize the distributed pump powers in kilowatt ytterbium-doped double-clad fiber laser

In this paper, we present the design of a new type of high speed electro-optic (EO) modulator based on long period fiber grating (LPG). The outer layer of the LPG is fabricated by material with high EO coefficient, and a special material with ultra-negative temperature coefficient is used for the temperature compensation. This
modulator can work steadily with low power microwave driver, its speed is very high and its cost is low. To our knowledge, this is the first time for a modulator designed with such a simple and effective structure.

Study on a high-speed polymer EO modulator-based LPG

The unified coupled-mode formalism derived from Maxwell's equation is employed to analyze the add/drop filters using a Bragg grating assisted mismatched coupler. An add/drop filter using a Bragg grating-assisted mismatched coupler is fabricated and tested. The maximum reflectivity, 3dB bandwidth, insert loss at the drop port and reflective loss at the input port of the filter are measured to be about 12 dB, 0.2 nm, 3.91 dB and −7.39 dB, respectively.

Shuisheng Jian

Papers

The design of Bragg fibers using genetic algorithm

Improvement in performance of L-band cladding pumped fiber amplifiers

Novel method to optimize the distributed pump powers in kilowatt ytterbium-doped double-clad fiber laser

Study on a high-speed polymer EO modulator-based LPG

The experimental fabrication of add/drop filters using a Bragg grating-assisted mismatched coupler