All-Fibre Ytterbium-Doped Photonic Crystal Fibre Laser with High Efficiency

A double-cladding ytterbium-doped photonic crystal fibre （PCF） with a 350-μm^2 effective area is fabricated. The measurement results show that the PCF has high absorption peak at 915 nm. Its fluorescence lifetime is 840μs. Laser experiments with all-fibre configurations are carried out with this fibre. A continuous-wave output power of 3.96 W is achieved with a 5.2 W launched pump power. The central wavelength of the output spectrum is 1080.22nm. The results show that the PCF laser has a high slope efficiency of 79.6% and light conversion efficiency of 76.2%.

The Design and Properties of G.656 Optical Fiber Waveguide Design

To prepare the G.656 optical fiber for the future＇s network, the methods of material design and waveguide design were applied to predict theoretic properties of the fiber. PCVD process was applied to manufacture the multi-layer GeO2, F co-doped SiO2 materials. The fiber properties were tested for the cut-off wavelength, MFD, dispersion, etc. The tested results agreed with the theoretic prediction.

Fibre Bragg Gratings Inscribed in Homemade Microstructured Fibres

Fibre Bragg gratings （FBGs） are inscribed in homemade microstructured fibres by the standard phase mask method. Enhanced couplings between the forward fundamental mode and backward cladding modes are obtained. The mode coupling and spectral characteristics are investigated experimentally. The cladding mode resonances can be affected by filling active materials into the air holes, which will be useful for the implementation of tunable photonic devices in optical fibre communication and sensing systems.

Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 rim, eight sam- ples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimen- tally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.

Direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters

Spatial modes have received substantial attention over the last decades and are used in optical communication applications.In fiber-optic communications,the employed linearly polarized modes and phase vortex modes carrying orbital angular momentum can be synthesized by fiber vector eigenmodes.To improve the transmission capacity and miniaturize the communication system,straightforward fiber vector eigenmode multiplexing and generation of fiber-eigenmode-like polarization vortices(vector vortex modes)using photonic integrated devices are of substantial interest.Here,we propose and demonstrate direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters.By exploiting vector vortex modes(radially and azimuthally polarized beams)generated from silicon microring resonators etched with angular gratings,we report data-carrying fiber vector eigenmode multiplexing transmission through a 2-km large-core fiber,showing low-level mode crosstalk and favorable link performance.These demonstrations may open up added capacity scaling opportunities by directly accessing multiple vector eigenmodes in the fiber and provide compact solutions to replace bulky diffractive optical elements for generating various optical vector beams.

High-gain integrated in-line few-mode amplifier enabling 3840-km long-haul transmission

An integrated few-mode erbium-doped fiber amplifier(FM-EDFA)with high modal gain is suitable for the in-line amplification in mode-division multiplexing transmission(MDM)systems.We first experimentally demonstrate a dual-stage integrated FM-EDFA supporting three linear polarization modes.Consisting of integrated passive components with low insertion losses,the FM-EDFA has a similar structure and performance to widely used commercial single-mode EDFAs.The averaged modal gain of 25 dB,the differential modal gain(DMG)of<1.1 dB,and noise figures of 5–7 dB are simultaneously achieved.In addition,the DMG of the 3M-EDF itself is~0.3 dB.Moreover,an MDM transmission experiment with the in-line few-mode amplification by our proposed FM-EDFA over a 3840-km few-mode fiber link for a 28-Gbaud quadrature phase-shift keying(QPSK)signal is demonstrated.

Few-mode fibre-optic microwave photonic links

The fibre-optic microwave photonic link has become one of the basic building blocks for microwave photonics.Increasing the optical power at the receiver is the best way to improve all link performance metrics including gain,noise figure and dynamic range.Even though lasers can produce and photodetectors can receive optical powers on the order of a Watt or more,the power-handling capability of optical fibres is orders-of-magnitude lower.In this paper,we propose and demonstrate the use of few-mode fibres to bridge this power-handling gap,exploiting their unique features of small acousto-optic effective area,large effective areas of optical modes,as well as orthogonality and walk-off among spatial modes.Using specially designed few-mode fibres,we demonstrate order-of-magnitude improvements in link performances for single-channel and multiplexed transmission.This work represents the first step in few-mode microwave photonics.The spatial degrees of freedom can also offer other functionalities such as large,tunable delays based on modal dispersion and wavelength-independent lossless signal combining,which are indispensable in microwave photonics.

Study on single-mode photonic crystal fibers in wide wavelength range

The comparatively large mode field single-mode photonic crystal fibers （PCFs） were fabricated, the lightwave from 600- to 1600-nm wavelength along this PCF could be transmitted in single mode. The manufacturing process technologies of the PCFs were exploited, and the drawing parameters of PCFs were also presented. The structure parameters on the single-mode performance of PCFs were theoretically studied, and in practice the design was proved. The measurements of cut-off wavelength and light intensity distri- bution showed that the PCF had comparatively wide single-mode operating wavelength range.

Amplifying Orbital Angular Momentum Modes in Ring-Core Erbium-Doped Fiber

Lots of research efforts have been devoted to increase the transmission capacity in optical communications using orbital angular momentum(OAM)multiplexing.To enable long-haul OAM mode transmission,an in-line OAM fiber amplifier is desired.A ring-core fiber(RCF)is considered to be a preferable design for stable OAM mode propagation in the fiber.Here,we demonstrate an OAM fiber amplifier based on a fabricated ring-core erbium-doped fiber(RC-EDF).We characterize the performance of the RC-EDF-assisted OAM fiber amplifier and demonstrate its use in OAM multiplexing communications with OAM modes carrying quadrature phase-shift keying(QPSK)and quadrature amplitude modulation(QAM)signals.The amplification of two OAM modes over four wavelengths is demonstrated in a data-carrying OAM-division multiplexing and wavelength-division multiplexing system.The obtained results show favorable performance of the RC-EDF-assisted OAM fiber amplifier.These demonstrations may open up new perspectives for long-haul transmission in capacity scaling fiber-optic communications employing OAM modes.

Review on developments of novel specialty fibers： performance, application and process

This paper reviews the development progress of optical fiber, the producing and application of the specialty optical fiber in the world. Finally it states the leading technology of optical fiber of the world. Specialty optical fibers are series of optical fiber which could satisfy special requirements. Recently, the rapidly growing need from fiber to the home （FTTH）, sensors, active optical link, energy conversion and delivery and fiber laser attracts researchers and optical companies to explore more possibilities of optical fiber and some novel specialty optical fibers were invented for the efforts. Bending insensitive optical fiber with the ability of extreme 3 mm bending diameter makes it possible to use the optical fiber as the electric wire in some extremely compact devices. Higher power was achieved in the fiber laser field with the development of rare earth doped fiber. Nanomaterials such as Au particles and ZnO nanostructures were utilized to extend the application in sensors and energy conversion. Pure silica design was commercialized to improve the radiation resistance of sensors based on fiber optics.

Experimental validation of domain-level gradient-based and hierarchical PCE-based routing and control in heterogeneous optical networks

A domain-level gradient-based routing （DLR） algorithm for heterogeneous optical networks with syn- chronous digital hierarchy and optical transport network domains is proposed and experimentally vali- dated. This algorithm classifies domains into groups with incremental levels on the basis of domain-level partitioning, and guides paths level by level along a gradient on the basis of interdomain routing tree evolution. The proposed algorithm is implemented in the hierarchical path computation element-based control architecture for connection provisioning. Testbeds with commercial and emulated nodes are es- tablished to verify the feasibility and performance of the algorithm. Experimental and emulation results show that DLR effectively performs in terms of network blocking probability, real time characteristics, and scalability.

Amplification of high-order azimuthal mode based on a ring-core Yb-doped fiber

In order to increase the number of amplified azimuthal modes in Yb-doped fiber(YDF),a multiple azimuthal modes amplifier based on a ring-core Yb-doped fiber(RC-YDF)was proposed and demonstrated.A home-made RC-YDF which can support 6 azimuthal mode groups was employed to amplify the signal mode at 1064 nm,using a core pump scheme.The amplification characteristics of 5 high-order azimuthal linear polarization(HA-LP)mode groups(LP_(11),LP_(21),LP_(31),LP_(41),LP_(51))were studied comprehensively.A more than 8 d B gain is obtained for each signal mode with 5 d Bm input power,and the associated differential modal gain between all modes is less than 1 d B.The intensity profiles of all modes are stable and well preserved during the process of amplification.