Fu Yong-Jun

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.

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.

Design and fabrication of triangular inner cladding double-clad ytterbium doped fibre for high power lasers

To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes to acquire high inner cladding numerical aperture are designed. Single mode and high power output of the fibre lasers need the double clad Yb doped fibre with large core. A fibre with annular refractive index distribution core and low numerical aperture to acquire a large mode area fibre core is designed and fabricated. Furthermore co-doping with aluminium (Al) has been used to improve the solubility of ytterbium (Yb) into silicate network and the core absorption coefficients of two Yb doped fibres are compared with different Al concentration experimentally.

Dynamic adaptive PMD compensation in a 40Gb/s OTDM system

An experiment of two-stages four degrees high-order polarization mode dispersion (PMD) compensation in 40 Gb/s optical communication system with a large PMD is reported. The former stage adopts polarization controller and fixed time-delayed line of polarization-maintaining fiber (PMF). The second stage consists of a polarization rotator and a tunable differential group delay (DGD) line that is based on magneto optical crystal. The second stage is used to compensate remnant first-order PMD. The PMD monitoring technique adopted degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. Some experimental results show that large PMD is compensated by this compensator in a 40 Gbits/s non-return-to-zero (NRZ) OTDM transmission systems. A significant improvement of system performance can be achieved in the eye pattern of a received signal. Most first-order compensating ability of the compensator is 35 ps. Second-order compensating ability of the compensator is 200 ps2 . The optimum compensating time is within several milliseconds