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 design criteria of the Panda-type erbium-doped polarization-maintaining fiber (EDPMF) are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. The structural parameters are optimized in terms of the design criteria. A Panda-type EDPMF has been manufactured. The fabrication process and the parameter control of the Panda-type EDPMF are in detail described. Its refractive index profile, birefringence and absorption spectra are experimentally investigated.

Design considerations for Panda-type erbium-doped polarization-maintaining fiber

The production mechanism of non-return-to-zero (NRZ), return-to-zero (RZ) and carrier suppressed return-to-zero (CSRZ) was analyzed theoretically in this paper. We compared the transmission performance of CSRZ with RZ and NRZ formats at 10 Gb/s system by numerical simulation. And we simulated the transmission model constructed with Erbium-doped fiber amplifier (EDFA) as the solo amplifier and the chirped fiber Bragg grating (CFBG) as the solo dispersion compensator used in the system. A practical 8 × 10 Gb/s 2 560 km transmitted experiment was conducted in straight line with these different modulation formats mentioned above and the experiment results show very good agreement with the result of computer simulation. The CSRZ format is more effective than other formats in the system, and involved only 2.5 dB power penalty cost in the practical 2 560 km error-free experiment. The results also show that CSRZ will help to optimize the transmitted results and reduce the transmitted penalty further.

Optimal modulation formats for 2 560 km optical transmission with low power penalty

A novel distributed all-optical multicast WDM fiber network based on a modified all-fiber multicast-capable OXC has been proposed and established. Configurable all-optical multicast including video and 10 Gb/s data are experimentally demonstrated.

Novel distributed all-optical multicast WDM fiber network: design and implementation

A theoretical investigation of bidirectionally dual-order pumped distributed Raman amplifiers is presented in detail, and comparisons with other Raman amplification schemes, i.e., bidirectional first-order pumping and Raman-plus-erbium-doped fiber hybrid amplification, are carried out at identical nonlinear phase shifts. The results show that symmetric bidirectional dual-order pumping can achieve the best optical signal-to-noise ratio performance by appropriate choice of the second-order pump wavelength and second-to-first-order pump power ratio for both short- and long-span conditions.

Bidirectionally dual-order pumped Raman amplifiers

A new type of highly nonlinear photonic bandgap fiber with modified honeycomb lattice is brought forward. Based on full-vector plane-wave method, the structure of bandgaps and the distributions of fundamental mode field are analyzed. Then its nonlinear coefficient is calculated, and the effect of each structural parameter on the nonlinear coefficient is discussed. At last, considering many factors synthetically, we make some optimization design of the structural parameters. It can be concluded that this new type of photonic bandgap fiber can gain the nonlinear coefficient of 30 W−1km−1.

Shuisheng Jian

Papers

Design considerations for Panda-type erbium-doped polarization-maintaining fiber

Optimal modulation formats for 2 560 km optical transmission with low power penalty

Novel distributed all-optical multicast WDM fiber network: design and implementation

Bidirectionally dual-order pumped Raman amplifiers

Research on highly nonlinear photonic bandgap fibers