A remnant chromatic dispersion monitoring method based on spectral shift of a semiconductor optical amplifier is proposed for a high speed optical communication system with carrier suppressed return to zero format and single-channel speed of 40 Gbit/s. The monitoring performance can be optimized by carefully selecting the bandwidth and center wavelength of the optical filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method is suitable for application in dynamical chromatic dispersion compensation of high speed optical communication systems.
We proposed the multipolar inserting zeros (MIZ) code for direct-sequence optical code division multiple access (OCDMA) systems. This code is designed to correspond with the judgment based on linear convolution. Simulation results showed that it can provide a lower multiuser interference than the conventional Gold sequence. With the same number of users, the bit error rate in the OCDMA system coded by MIZ can be reduced by several decuples than that coded by Gold, and the source power needed to reach a BER of 1×10?9 can also be reduced by several decibels. So the performance of OCDMA can be improved.
A chirped, phase-shifted structure is demonstrated for compact multi-wavelength DFB fiber laser at room temperature for the first time. The chirped structure provides separated resonance cavities and then the stable multi-wavelength operation. The equivalent phase shift method is demonstrated to realize the desired chirp and phase shifts simply and flexibly. A 44pm-spaced, dual-wavelength DFB fiber laser is then achieved experimentally, which is the narrowest spacing ever reported for a compact multi-wavelength fiber laser.
We have developed a thermally tunable module to compensate polarization mode dispersion (PMD) and chromatic dispersion (CD) simultaneously. In this module, twins of linearly chirped fiber Bragg gratings (LCFBGs) are used to compensate PMD and one non-linearly chirped FBG (NLCFBG) is used to compensate CD in 40Gb/s optical fiber communication system. The fiber Bragg gratings are coated with uniform thin metal film, and by changing the applied current through the film, the tunable compensation for PMD and CD is achieved. The fabrications of the LCFBG and NLCFBG are both utilizing the linearly chirped phase mask, making the fiber Bragg gratings easy to obtain.
In this paper, an optical code division multiple access (OCDMA) system is demonstrated. The ultrashort light pulse is encoded and then decoded by amplitude sampled fiber Bragg gratings with equivalent phase shift (EPS). Compared with traditional superstructured fiber Bragg grating (SSFBG) with real phase shift (RPS), FBG with EPS is much easier to fabricate. In our experiment, it shows its full ability to perform encoding and decoding in OCDMA systems, and good encoding/decoding performance is achieved.
Polarization mode dispersion can decrease the performance of the fiber-optic transmission seriously. Thus the compensation of Polarization mode dispersion is a critical issue in fiber optics. In this paper, a novel Polarization mode dispersion compensator is suggested and demonstrated based on a special-design fiber Bragg grating. A polarization mode dispersion compensation grating with 10-156ps dynamical span and flat-top response is first reported based on the combination of reconstruction algorithm and the equivalent-chirp method. A 10-Gb/s system experiment using the tunable PMD compensator shows the power penalty of BER at is about 1.2dBwhen the PMD of the system is 60ps.
A cost-effective tunable dispersion compensator using reconstruction-equivalent-chirp method is fabricated. Only uniform phase mask, sub-micron precision and uniform thin metal film are required in the fabrication. The group delay ripple is less than 14 ps during the whole tuning range. An experiment in 40-Gb/s system is demonstrated with a power penalty of 0.7dB.
We design a novel tunable interchannel dispersion-slope compensator using a single broad-band nonchannelized sampled fiber Bragg grating (FBG) with chirp in the sampling period. Tunability of the dispersion-slope can be achieved by stressing or heating the grating uniformly, which has a third-order time-delay variation with wavelength, thereby causing a second-order variation in dispersion. By using the equivalent-chirp method, i.e. by chirping the sampling function, we get the time-delay within -1st order Fourier reflection band and consequently realize dispersion-slope compensator.
A new instrument to measure stokes vectors using an electro-drived polarization controller and a polarizer based on "TDM" is demonstrated. Using this instrument as well as data fitting and interleaving technique higher-order PMD is detailed.
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