A 20Gb/s polarization-insensitive all-optical wavelength switching system for high-speed free-space optical communication (FSO) network is experimentally demonstrated All-optical wavelength conversion (AOWC) is implemented using four-wave mixing (FWM) by highly-nonlinear fiber (HNLF). In the experimental setup, a simple actively mode-locked fiber ring laser (AML-FRL) with repetition frequency from 1 to 15 GHz is used to generate eight 2.5Gb/s tributary signals, which are multiplexed into one 20Gb/s optical data stream. At the receiver, the 20 Gb/s OTDM data stream is demultiplexed down to 2.5 Gb/s via a polarization-insensitive FWM scheme. The whole space communication distance is over 10 meters in building hallway. The experimental results show that this system can stably run over 24 hours at 10<sup>-9</sup> BER level, thus the proposed architecture can work at higher rate with wavelength-division multiplexing (WDM) and high order modulation schemes.
Proc. SPIE. 9679, AOPC 2015: Optical Fiber Sensors and Applications
KEYWORDS: Signal attenuation, Telecommunications, Optical communications, Free space optics, Optical networks, All optical signal processing, Information security, Quantum communications, Network security, Channel projecting optics
Secure optical communication technologies are important means to solve the physical layer security for optical network. We present a scheme of secure optical communication system by all-optical signal processing technique. The scheme consists of three parts, as all-optical signal processing unit, optical key sequence generator, and synchronous control unit. In the paper, all-optical signal processing method is key technology using all-optical exclusive disjunction (XOR) gate based on optical cross-gain modulation effect, has advantages of wide dynamic range of input optical signal, simple structure and so on. All-optical XOR gate composed of two semiconductor optical amplifiers (SOA) is a symmetrical structure. By controlling injection current, input signal power, delay and filter bandwidth, the extinction ratio of XOR can be greater than 8dB. Finally, some performance parameters are calculated and the results are analyzed. The simulation and experimental results show that the proposed method can be achieved over 10Gbps optical signal encryption and decryption, which is simple, easy to implement, and error-free diffusion.
A satellite laser communications network structure with two layers and multiple domains has been proposed, which performance has been simulated by OPENT. To simulation, we design several OPNET models of the network’s components based on a satellite constellation with two layers and multiple domains, as network model, node model, MAC layer protocol and optical antenna model. The network model consists of core layer and access layer. The core network consists of four geostationary orbit (GEO) satellites which are uniformly distributed in the geostationary orbit. The access network consists of 6 low Earth orbit (LEO) satellites which is the walker delta (walk-δ) constellation with three orbit planes. In access layer, each plane has two satellites, and the constellation is stably. The satellite constellation presented for space laser network can meet the demand of coverage in the middle and low latitude by a few satellites. Also several terminal device models such as the space laser transmitter, receiver, protocol layer module and optical antenna have been designed according to the inter-satellite links in different orbits t from GEO to LEO or GEO to ground. The influence to network of different transmitting throughput, receiving throughput, network protocol and average time delay are simulated. Simulation results of network coverage, connectivity and traffic load performance in different scenes show that the satellite laser network presented by the paper can be fit for high-speed satellite communications. Such analysis can provide effective reference for the research of satellite laser networking and communication protocol.
We present simulation results for a 5 Gb/s optically pre-amplified, differential phase shift keying communication
system achieving -48.1 dBm (about 24.7 photons/bit) receiver sensitivity at 10<sup>-9</sup> bit-error-rate and using an optical delay
line interferometer made by ourselves with 1 bit delay as the demodulator. The system is also experimental tested and
sensitivity of the receiver is -36.5 dBm (about 106.6 photons/bit). The experimental results have some penalty in
sensitivity comparing to the results in the simulation because the 1 bit delay interferometer is sensitive to the
environment such as temperature, tremble and so on. To our knowledge if the interferometer is well designed and
optimized, the experimental results can correspond with the simulative results and an optically pre-amplified direct
detection DPSK receiver with high sensitivity can be realized.
This paper presents a compact frequency-independent equivalent-circuit model for mmW characteristics of lithium
niobate (LiNbO<sub>3</sub>) optical modulator, taking the skin effect, and substrate effect into consideration. Equivalent-circuit
model with only ideal lumped elements represents the broadband electrical response of LiNbO<sub>3</sub> modulator. A 4-long
ladder model is used to model the skin effect. Coupling capacitor is used to simulate the substrate coupling from the
CPW to the buffer and LiNbO<sub>3</sub> substrate. Lumped-element circuit model was cascaded to model the distributive skin
effect, transmission attenuation, and substrate effect. The equivalent-circuit models are fully SPICE compatible and can
be incorporated directly into common circuit simulators and microwave design tools.