Incompatibility of polarization-division multiplexing with wavelength-division multiplexing in soliton-transmission systems

In a recent experiment it was demonstrated that polarization-division multiplexing was incompatible with wavelength-division multiplexing. We discuss a theoretical model that explains this result.     

Electrically controlled diffraction of light by reflection holograms in an LiNbO3 crystal

A theoretical and experimental investigation is made of the electrical selectivity of reflection volume holograms recorded in a LiNbO₃ crystal using a near-optimum geometry. An analysis is made of the factors limiting electrical multiplexing. Fiz. Tverd. Tela (St. Petersburg) 40, 1038–1041 (June 1998)     

光波分复用实验的改进和扩展

利用自聚焦透镜代替集成的波分复用器件,对2路波分复用实验结构进行了改进,并在实验中增加光谱仪用于观察光纤中的光谱.通过上述改进,使学生进一步了解波分复用器内部结构,加深对复用和解复用的理解.     

Substrate-strain-induced tunability of dense wavelength-division multiplexing thin-film filters

Classic dense wavelength-division multiplexing thin-film filters can be spectrally tuned through the substrate's strain. We analyze the theoretical shift of the design wavelength of a narrow-bandpass filter when uniform, uniaxial compressive stress is applied to the substrate, and we compare calculated sensitivity with experimental data. We measure the transmittance shape of a 200-GHz standard filter for several loading cases to quantify the increase of insertion losses.     

Longitudinal distortion in images reconstructed by reflection holograms

Reflection holograms recorded on photographic materials usually reconstruct an image at a shorter wavelength than that at which they were recorded. As a result, the lateral and longitudinal magnifications of the reconstructed image are not the same and the image appears distorted. It is shown that this distortion can be minimized by a proper choice of the recording geometry. The residual aberrations of the image are discussed.     

Demonstration of massive wavelength-division multiplexing over transoceanic distances by use of dispersion-managed solitons

By combining a special dispersion map that has nearly constant path-average dispersion, a hybrid amplification scheme involving backward-pumped Raman gain, and sliding-frequency guiding filters, we have demonstrated massive wavelength-division multiplexing at 10 Gbits/s per channel, error free (bit-error rate, 相似文献   

Reduction of collision-induced timing jitter in dense wavelength-division multiplexing by the use of periodic-group-delay dispersion compensators

We show how replacement of a modest fraction of the usual fiber-based dispersion compensation with a periodic-group-delay dispersion-compensating module can result in a drastic reduction in collision-induced timing jitter in dense wavelength-division multiplexing with dispersion-managed solitons. The principal mechanism here is a correspondingly large reduction in the net path over which a pair of colliding pulses interact.     

Characteristics of the reconstructed image upon multiplexing on-axis holograms

A comparative analysis of the experimental data on recording and multiplexing holograms, including speckle holograms, by an axial scheme is presented. The contrast and signal-to-noise ratio in the images reconstructed are compared. It is demonstrated that the thickness of the photosensitive material has an effect on the image quality during the recording of filamentary holograms.     

Ring-resonator filters in silicon oxynitride technology for dense wavelength-division multiplexing systems

The design and characterization of ring-resonator-based filters with free spectral ranges of 100 and 50 GHz by use of SiO(x)N(y) technology is presented. Fiber-to-fiber insertion losses of 4.4 dB on the drop port and 2.1 dB on the through port have been achieved for a single-ring filter. An interleaver filter for a 25-GHz spaced dense wavelength-division multiplexing system with two cascaded rings is demonstrated. The filter has a 7.4-GHz bandwidth at -1 dB and an extinction ratio of 15 dB and is polarization independent.     

Photon statistics of amplified spontaneous emission in a dense wavelength-division multiplexing regime

The photon statistics of amplified spontaneous emission in the few-modes regime and in single mode, conditions that are typical of dense wavelength-division multiplexing transmission, have been experimentally proved by direct detection. The dependence of the degeneracy factor for the Bose-Einstein distribution on the degree of second-order coherence of light is stated. The theoretical dependence of the number of amplified spontaneous emission modes on the ratio between the optical channel and the detector bandwidths has also been confirmed by experiments, thus quantifying the loss of validity of asymptotic approximations when they are extended to the few-modes regime.     

Promising compact wavelength-tunable optical add-drop multiplexer in dense wavelength-division multiplexing systems

We design and model a highly compact and tunable optical add-drop multiplexer (OADM) device that consists of long-period gratings and piezoelectric ceramic fiber stretchers. The proposed OADM shows that 50 dense wavelength-division multiplexing channel signals can be selected in the wavelength range from 1526.25 to 1563.75 nm with 0.75-nm channel spacing, which covers the whole C-band gain spectrum of an erbium-doped fiber amplifier. The cross talk between channels is less than -39 dB, and the total insertion loss of the device is approximately 0.24 dB, which includes the splicing losses, the mode mismatching loss, and the expected losses in the two side-by-side coupled fibers.     

High longitudinal selectivity of shifting multiplexing in volume holograms

High longitudinal selectivity of the shifting multiplexing with spherical reference wave is proposed and demonstrated. A simplified method based on wave optics is used for calculating the selectivity, and the result fits well the experimental measurement. Under the paraxial condition, a simple formula for the longitudinal selectivity is introduced. With use of an object lens with effective NA=0.817, we obtain that an FWHM of selectivity is as small as 1 μm.     

Periodic dispersion management in soliton wavelength-division multiplexing transmission with sliding filters

We compare the performance of dispersion-managed fibers with that of dispersion-decreasing fibers and of fibers with uniform dispersion in filtered soliton wavelength-division multiplexing transmission. Alternating-sign dispersion management allows us to achieve values of collision-induced timing jitter that are comparable with what can be achieved by use of dispersion-decreasing fiber and are lower for some parameter values.     

Coupled-mode analysis of fiber-optic add drop filters for dense wavelength-division multiplexing

We present a coupled-mode theory of fiber-optic add-drop filters, which involve directional coupling between two fibers combined with fiber Bragg gratings defined inside the coupling region. The analysis self-consistently accounts for both the directional and the reflection coupling, and the propagation constants and structure of the supermodes of the combined structure are derived. We present a detailed analysis of a filter design based on identical fibers. The calculated device parameters satisfy the requirements for dense wavelength-division multiplexing applications.     

Electric field selectivity and multiplexing of volume holograms in LiNbO3

Theoretical and experimental investigations of electric field multiplexing and selectivity of reflection volume holograms in LiNbO₃ are reported. Recording of at least five holograms is demonstrated. Equivalent spectral selectivity (5Ƽ.5 pm for the case of three electrically tunable holograms and (5ǁ pm for the case of five electrically tunable holograms are estimated.     

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.