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

A vectorial finite element method (VFEM) is adopted to investigate the novel single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler which has asymmetric dual-core and two lines of enlarged air holes. It is demonstrated that the SPSM region of the designed fiber can be more than 250 nm wide with a set of optimized air-hole parameters and the width of the SPSM region could change slightly by fine adjustment of the inner large air holes. The coupling length between the odd and even x-polarization modes is also investigated through fine-tuning the large and small air-hole diameters.

An asymmetric dual-core single-polarization single-mode photonic crystal fiber coupler

In this article, we introduce the fabrication of apodized chirp FBG by scanning method, which monitored by computer. The FBGs are 13.5 cm long with 3 dB bandwidth 0.851 nm and 0.423 nm, respectively. The reflectivity are flatness with ripple coefficient less than 0.7 dB and the ripple coefficient of time delay are less than 20 ps. The dispersion of 10 Gb/s 100 km and 200 km G.652 optical fiber is compensated by the grating respectively, and more than 98% dispersion is compensated. (The original pulse width is 36.78 ps; after compensation the pulse width is 37.23 ps and 37.19 ps). With 10-10 BER, the power penalty of the system is 0 dB.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Dispersion compensation of optical fiber Bragg grating (FBG) with low ripple coefficient

A high concentration silica host Erbium Doped Fiber with Bismuth-Gallium-Aluminum co-doped was fabricated. The absorption coefficient of this fiber was up to 19dB/m at the wavelength of 980nm and 42dB/m at 1530nm. Ring structure lasers with different fiber lengths were presented. Their output characteristics were measured and analyzed.

High-concentration erbium-doped fiber-based short cavity ring lasers

A new but simply implemented all-optical clock enhancement scheme for nonreturn-to-zero (NRZ) data streams utilizing a semiconductor optical amplifier (SOA) and a chirped fiber Bragg grating (CFBG) is presented. The clock-to-carrier suppression ratio is highly improved by more than 23 dB by the CFBG compared with the value obtained only including the SOA. In addition, the clock is recovered based on stimulated Brillouin scattering (SBS). The clock recovery for the NRZ signal following various lengths of single-mode fiber (SMF) is numerical simulated and also demonstrated experimentally. The recovered clock degrades as the length of fiber increases. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2764–2768, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23787

All‐optical clock enhancement for transmitted NRZ data streams based on CFBG

In this paper, experimental and theoretical investigations of TOAD system performance are implemented. 80Gb/s to 10Gb/s all-optical demultiplexing by the TOAD is demonstrated successfully. Based on the travelling wave model, the non-ideal problems encountered in the experiment are analyzed. The results show the position of SOA is no need to be strictly placed beside the loop midpoint, due to the switching window can be periodically generated with asymmetry values of SOA, and the position of switching window can be adjusted by varying the temporal deviation between counter-propagation signals. Furthermore, the unperfected coupling ratio and the synchronization jitter between the signal and control are crucial limits for the demultiplexing application in 160Gb/s OTDM system.

Shuisheng Jian

Papers

An asymmetric dual-core single-polarization single-mode photonic crystal fiber coupler

Dispersion compensation of optical fiber Bragg grating (FBG) with low ripple coefficient

High-concentration erbium-doped fiber-based short cavity ring lasers

All‐optical clock enhancement for transmitted NRZ data streams based on CFBG

Experimental and theory study the system performance of TOAD using for demultiplexing in 160Gb/s OTDM transmission system