A phase-shift fiber Bragg grating with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands. The sampled Moir

Broadband and gain-flatted Raman fiber amplifier (RFA) is one of the key devices of dense-wavelength-division-multiplexing systems. Its amplification mechanism, pump schemes and the characteristics etc are introduced in the paper. The methods of realizing the broadband and gain flatted RFA mare analyzed. We made the theoretical and experimental investigation for RFA. Our researching results showed the RFA has the outstanding features for DWDM transmission system and are the good reference to design and use of RFA.

In this paper the direct spreading/wavelength hopping (DS/WH) eo-/de-coding scheme for optical code-division multiple access (OCDMA) is proposed. The system structure is designed and analyzed. A new code sequence-wavelength hopping extended quadratic congruence for prime code (WH EQC/prime code)-is adopted. It is shown that the code capability can be increased by increasing the number of discrete wavelengths or by employing asymmetric systems with different prime numbers for spreading and hopping (Ps and Ph). The Synchronous signal is designed and analyzed It is very easy for user to decode synchronously. The performance of the system is investigated and it is shown that the en-/de-coding scheme and system structurn are feasible.

在二次方一致性的基础上,构造了一种容量大、自相关和互相关特性好的码族。研究表明,采用这个码族的光码分多址(Optical CDMA)系统比波分复用(WDM)系统拥有大得多的用户数。而且这个码族很适合于异步和多比特率接入的光码分多址系统。 据我们了解,这种码字用于在光码分多址非相干频域编制中为首次被提出。

The design of a multi-channel fibre Bragg grating to compensate simultaneously the fibre dispersion and dispersion slope is proposed and analyzed. It is found that constituent gratings with equal length would result in unequal channel bandwidth and large band edge side lobes in broad bandwidth channels due to large dispersion slope. To overcome these short-comings, we propose a new design procedure in that both the physical length and apodization function of the constituent gratings be allowed to vary. This results in a multi-channel grating with equal bandwidth and negligible band edge side lobes. Of course this grating compensates both the fibre dispersion and dispersion slope very well.

Gain, gain saturation, optical signal-to-noise ratio (OSNR) and pump power conversion efficiency (PCE) of co-and counter-pumped Raman fiber amplifiers (RFAs) were investigated and compared experimentally in this paper. Results show that obvious OSNR improvement can be achieved with co-pumped RFAs. Compared with the counter-pumped scheme, the co-pumped solution has more severe gain saturation. For both two pumping schemes, PCE decreases as the input power increases. However, PCE decreases faster for the co-pumped RFAs.

We analyzed the effect of various normal distributed nonuniformities of sampled fiber Bragg gratings on the reflective spectra and group time delay. Through numerical simulations, we have drawn the following conclusions: (1) the magnitude of nonuniformity with normal distribution of fiber average refractive index modulation δneff greatly influences the characteristics of both reflective spectra and group time delay, and the suggested precision of that varies from 20% to 10%; (2) the nonuniformities of sampling periods P and sampling lengths L are very important factors that influence the characteristics of the group time delay, and the accepted tolerance of dimensional precision of both sampling period P and sampling length L are about ±4 microns; (3) the tolerance of the nonuniformity of the sampling period’s chirp coefficient cs is high, and its precision can be as great as 100% with small adverse effects.

A novel compact BNI architecture in free space is composed of symmetrical arrays of binary phase grating having advantages of high spatial density, no coupling material, wide bandwidth., low insertion loss, tow crosstalk, compaciting system, easy cascading. erc..

In this paper, we propose a new en-/de-coding scheme of spreading time OCDMA utilizing the dispersion of grating and filter in frequency domain. The key components of the scheme are grating pair, Fourier transformation lens, phase filter etc. The results of design and calculation are shown that the spreading time of input pulse can be up to nanosecond- duration and the phase filter can provide pseudo-noise bursts in time domain. The requirement s for Laser and optical detection equipment in the scheme are reduced. So the new scheme proposed by us is effective for OCDMA en-/de-coding of coherent ultra-short pulses.