Ning Tigang

Performance of a 10-Gbit/s Transmission System over 1500 km G.652 Fibre Compensated by Cascaded Narrow-Band Chirped Fibre Bragg Gratings

We obtain the error-free transmission of an 8?10?Gb/s signal over a 1500?km G.652 fibre by means of significantly improving the quality of narrow-band chirped fibre Bragg gratings (FBGs). Asymmetric apodization is one of the powerful measures to improve the quality of gratings. Wavelength-dependent transmission performance is also observed. The experimental results indicate that the total in-band local dispersion deviation of the cascaded gratings in each channel could be a good indicator of the performance degradation tendency at different operating wavelengths, which further reveals the potential of local dispersion deviation as a performance evaluating indicator of chirped FBGs.

Suppression of the interactions between fibre gratings used as dispersion compensators in dense wavelength-division multiplexing systems

Chirped fibre Bragg gratings (CFBGs) are required to be concatenated to compensate the fibre dispersion in the dense wavelength-division multiplexing (DWDM) systems. When the channel spacing is small, the performance of CFBGs is degraded, which restricts the usage of fibre gratings. The origin of the interactions between the gratings is analysed and methods of suppressing the interactions are also proposed.

Anamorphic beam concentrator for linear laser-diode bar

An anamorphic beam concentrator for linear laser-diode (LD) bar is presented. It consists of a tapered SiO2-rod with skewed and curved surface. The principle and applicability of this device are numerically investigated by ZEMAX and experimentally illustrated for the specific example of the linear LD bar. Results show that a relative symmetrical output beam spot is produced at the output facet of the rod and the intensity and spatial fluctuations in the input beam are compensated at distance of 20cm from the output facet.

FTTH - a promising broadband technology

With the extraordinary increase of bandwidth requirement nowadays, service providers are compelled to push fiber deeper into the access networks in order to be able to offer the emerging services that customers are demanding. Fiber-to-the-home (FTTH) networks have always been the ultimate solution to a future broadband access network. In recent years, several technological developments have brightened the outlook on FTTH. The paper highlights these changes, and presents architectures that may be successfully deployed in the near future. The author estimates the value of FTTH and the foreground of its application and development in the world market.

The system of L-band 2×10 Gb/s WDM transmission over conventional single mode fibre with 600 km by chirped fibre Bragg gratings dispersion compensation

A chirped fibre Bragg grating according to ITU-T suggested L-band (2nd channel λ1 = 1570.83 nm; 80th channel λ2 = 1603.57 nm) with more than 1800 ps/nm single channel dispersion compensation is presented in this paper, of which the cladding mode loss, the delay curve ripple and the power fluctuation of the reflected spectrum are less than 0.5 dB, 50 ps and 0.25 dB, respectively. With this new FBG as dispersion compensation device, a 2 × 10 Gb/s wavelength division multiplexing (WDM) L-band transmission of 600 km based on conventional single mode fibre (G.652 fibre) is performed without forward error correction. The bit error rate (BER) is less than 10−12 and the power penalties of the 2nd and 80th channel of L-band are 1.8 dB and 2.0 dB, respectively.

Analysis and Measurement of the Displacement Sensor Based on an Up-tapered Mach—Zehnder Interferometer

A displacement sensor based on an up-tapered Mach—Zehnder interferometer (MZI) is proposed and demonstrated experimentally. For this purpose, a fiber MZI is fabricated by using a commercial fusion splicer. Then the transmission spectra of the sensors with different middle fiber lengths are measured by bending the MZIs with different movements of the moving stage. The maximum sensitivity of 2.457 nm/mm is achieved while the shifting of the moving stage changes from 3mm to 3.5 mm. Note that this kind of up-taper configuration is strong in strength, easy to fabricate and low in cost.

Design and Fabrication of an Er-Doped Silica Optical Fiber with Six Photosensitive Subcores

A type of multi-core Er-doped photosensitive silica optical fiber (MC-EDPF) is proposed and fabricated, in which a high consistency Er-doped core is surrounded by six high consistency Ge-doped cores. The multi-core design can overcome the difficulties encountered in the design and fabrication of single-core EDPFs through a modified chemical vapor deposition method combined with solution doping technology, and there is a conflict between high consistency Er doping and high consistency Ge doping. The absorption of MC-EDPFs achieved 15.876 dB/m at 1550nm and 10 dB/m at 980nm. The reflectivity of the fiber Bragg gratings (FBGs) written directly on the MC-EDPFs is as much as 96.84%.

Ultra-Long Haul L-Band WDM Transmission over a Standard Single-Mode Fibre Loop Using DCF+CFBG Hybrid Dispersion Compensation

We demonstrate a 10.7 Gb/s-line-rate L-band wavelength-division-multiplexer (WDM) loop transmission over a 1890-km standard single-mode fibre (SSMF) with a 100-km amplifier spacing as well as non-return-to-zero (NRZ) format. The dispersion compensating fibre (DCF) plus chirped fibre Bragg grating (CFBG) is employed for hybrid inline dispersion compensation. The power penalty of each channel is less than 3 dB after three-loop transmission. The experimental results show that high-performance CFBGs can be successfully used in ultra-long haul (>1000 km) WDM systems. We also point out that the all-CFBG compensation scheme is not suitable for re-circulating loop transmissions.

Design and fabrication of Panda-type erbium-doped polarization-maintaining fibres

To obtain the stable operation of erbium-doped fibre laser, the simple and ideal technology is adopted by use of the erbium doped polarization maintaining fibre (EDPMF). The design criteria of the Panda-type EDPMF are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. Four groups of optimum structural parameter combinations are determined in terms of the design criteria. Two kinds of the Panda-type EDPMFs are selected to be fabricated. The fabrication process and the parameter control of the Panda-type EDPMFs are presented in detail. Their refractive index profiles, birefringence and absorption spectra are experimentally investigated. The absorption coefficient of the EDPMF, whose core is co-doped with Bi, Ga, Al and Ge, is about 57.9 dB/m at 1.53 μm. Co-doping Bi, Ga and Al can greatly increase the erbium concentration in the silica-based fibre. The high birefringence is obtained for the Panda-type EDPMF. The group birefringence of the EDPMF, whose outer cladding diameter is 125 μm, is about 4.8×10−4.

Compensating the first-order PMD by using a novel tunable compensator

With increasing bit-rate PMD (polarization mode dispersion) is becoming major system impairment. As the birefringence of a fiber changes randomly along a fiber link and the state-of-polarization (SOP) of an optical signal changes, with environmental conditions, PMD effects on the data signal are stochastic and time varying. Consequently, compensation of PMD, especially for the first-order PMD is necessary to maintain adequate performance in long-haul systems at a high bit rate of 10 Gbit/s or beyond. In this paper, we successfully demonstrated automatic and tunable compensation for first-order polarization-mode dispersion. Furthermore, we reported the statistical assessment of this tunable compensator at 10 Gbit/s. Experimental results, including bit error rate measurements, are successfully compared with theory, therefore demonstrating the compensator efficiency at 10 Gbit/s. The first-order PMD was max 274 ps before PMD compensation, and it was lower than 7ps after PMD compensation.