A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

Microwave photonics, which brings together the worlds of radiofrequency engineering and optoelectronics, has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future. The technology makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks. Here we introduce the technology to the photonics community and summarize recent research and important applications.

Microwave photonics combines two worlds

The history, fabrication, theory, numerical modeling, optical properties, guidance mechanisms, and applications of photonic-crystal fibers are reviewed

Photonic-Crystal Fibers

Photonic crystal fibers are a new class of optical fibers. Their artificial crystal-like microstructure results in a number of unusual properties. They can guide light not only through a well-known total internal reflection mechanism but using also photonic bandgap effect. In this paper different properties possible to obtain in photonic crystal fibers are reviewed. Fabrication and modeling methods are also discussed.

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Photonic Crystal Fibers

An applications-oriented review of optical parametric amplifiers in fiber communications is presented. The emphasis is on parametric amplifiers in general and single pumped parametric amplifiers in particular. While a theoretical framework based on highly efficient four-photon mixing is provided, the focus is on the intriguing applications enabled by the parametric gain, such as all-optical signal sampling, time-demultiplexing, pulse generation, and wavelength conversion. As these amplifiers offer high gain and low noise at arbitrary wavelengths with proper fiber design and pump wavelength allocation, they are also candidate enablers to increase overall wavelength-division-multiplexing system capacities similar to the more well-known Raman amplifiers. Similarities and distinctions between Raman and parametric amplifiers are also addressed. Since the first fiber-based parametric amplifier experiments providing net continuous-wave gain in the for the optical fiber communication applications interesting 1.5-/spl mu/m region were only conducted about two years ago, there is reason to believe that substantial progress may be made in the future, perhaps involving "holey fibers" to further enhance the nonlinearity and thus the gain. This together with the emergence of practical and inexpensive high-power pump lasers may in many cases prove fiber-based parametric amplifiers to be a desired implementation in optical communication systems.

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Fiber-based optical parametric amplifiers and their applications

A low-loss and highly birefringent polarization maintaining photonic crystal fiber has been fabricated. The fiber loss and modal birefringence at 1550 nm were 1.3 dB/km and 1.4×10-3, respectively.

Optical properties of a low-loss polarization-maintaining photonic crystal fiber

An optical fiber that guides only one polarization mode of a light signal is realized by using highly birefringent pure silica photonic crystal fiber. The fiber guides only one polarization mode at wavelengths longer than 1450 nm. A polarization dependent loss of 196 dB/km with a 28 dB/km transmission loss is achieved at a wavelength of 1550 nm.

Absolutely single polarization photonic crystal fiber

A 3 Tbit/s (160 Gbit/s × 19 channels) optical signal has been successfully transmitted over 40 km of dispersion-shifted fibre Low noise supercontinuum signal pulse sources and 70 nm bandwidth tellurite-based optical amplifiers are used for 3 Tbit/s signal generation and amplification

3 Tbit/s (160 Gbit/s × 19 channel) optical TDM and WDM transmission experiment

We demonstrate the generation of symmetrical supercontinuum of over 40 nm in the 1.55 m region (1540 - 1580 nm) by injecting 1562 nm, 2.2 ps, 40 GHz optical pulses into a 200 m-long, dispersion-flattened polarization-maintaining photonic crystal fiber. The chromatic dispersion and dispersion slope of the fiber at 1.55 m are -0.23 ps/km/nm and 0.01 ps/km/nm2, respectively. This is the first report of 1.55 m band supercontinuum generation in a dispersion-flattened and polarization-maintaining photonic crystal fiber.

Supercontinuum generation at 1.55 m in a dispersion-flattened polarization-maintaining photonic crystal fiber.

0.25 – 0.67 ps optical pulses with time-bandwidth products of 0.11 – 0.14 are generated at 6.3 GHz over 1530 – 1562 nm by spectrally filtering the chirp-compensated supercontinuum generated by 2.5 ps Er3+-doped fibre laser pulses. The proposed scheme features a multiwavelength GHz output over a continuous wavelength range, and offers a wide variety of applications in ultrafast all-optical TDM/WDM networks.

Satoki Kawanishi

Papers

Optical properties of a low-loss polarization-maintaining photonic crystal fiber

Absolutely single polarization photonic crystal fiber

3 Tbit/s (160 Gbit/s × 19 channel) optical TDM and WDM transmission experiment

Supercontinuum generation at 1.55 m in a dispersion-flattened polarization-maintaining photonic crystal fiber.

Transform-limited, femtosecond WDM pulse generation by spectral filtering of gigahertz supercontinuum