The Possibility of Applying Spectral Redundancy in Coherent DWDM Systems for Increasing the Data Transmission Rate and Decreasing Nonlinear Effects and Double Rayleigh Scattering with Great Security of Data

A new method coherent DWDM system has been proposed. Standard method uses 90 wavelengths with channel capacity 100 G, so total capacity amounts to 9 Terabit, optical power is P. New “channel super” (CS) consists of 15 wavelengths, number of CS is 6, so total number of wavelengths is 90 too, total capacity is 6 Terabit, but optical power is 4/15P. Over ULH and EULH markets, standard approach will be forced to reduce the total capacity to 2.4 Terabit with optical power 4/15P as in proposed method. But the new can reach 6 Terabit with the same optical power 4/15P.

Applications of weakly-coupled few-mode fibers[Invited]

Space-division multiplexing(SDM)has attracted significant attention in recent years because larger transmission capacity is enabled by more degrees of freedom(DOFs)in few-mode fibers(FMFs)compared with singlemode fibers(SMFs).To transmit independent information on spatial modes without or with minor digital signal processing(DSP),weakly-coupled FMFs are preferred in various applications.Several cases with different use of spatial DOFs in weakly-coupled FMFs are demonstrated in this work,including single-mode or mode-groupmultiplexed transmission,and spatial DOFs combined with time or frequency DOF to improve the system performance.

Frequency synthesis of forced opto-electronic oscillators at the X-band

Ultra-low phase noise performance is required for frequency agile local oscillators, which are the core for high resolution imagers, spectrum analyzers, and high speed data communications. A forced opto-electronic oscillator （OEO） benefits from frequency stabilization techniques for realizing a clean and low phase noise source at micro- wave and millimeter wave frequencies. Forced oscillation techniques of self-injection locking and self-phase lock loop are combined to provide an ultra-low oscillator phase noise both close-in and far-away from the carrier frequency, while a tunable yttrium iron garnet microwave filter combined with a wavelength tuned transversal filter are employed to implement both coarse and fine frequency tuning for a tunable X-band OEO. A phase noise of -137 dBc/Hz at an offset frequency of 10 kHz is achieved covering the frequencies of 9 to 11 GHz with a fine frequency tuning resolution of 44 Hz/pm and coarse tuning of 25 MHz/mA. Moreover, the long term stability of the output signal is tested, and a maximum frequency drift of 2 kHz is measured within 60 min for the X-band synthesizer.

Photonics-assisted compressive sampling system for wideband spectrum sensing

Compressive sampling （CS） has attracted considerable attention in microwave and radio frequency （RF） fields in recent years. It enables the acquisition of high-frequency signals at a rate much smaller than their Nyquist rates. Combined with photonics technology, traditional CS systems can significantly enlarge their operating bandwidth, which offers great potential for spectrum sensing in cognitive radios. In this Letter, we review our recent work on photonic CS systems for wideband spectrum sensing. First, a proof-of-concept photonics-assisted CS system is demonstrated; it is capable of acquiring numerous radar pulses in an instantaneous bandwidth spanning from 500 MHz to 5 GHz with a 500-MHz analog-to-digital converter （ADC）. To further reduce the acquisition bandwidth, multi-channel photonics-assisted CS systems are proposed for the first time, enabling the acquisition of multi-tone signals with frequencies up to 5 GHz by using 120-MHz ADCs. In addition, the system bandwidth is increased from 5 to 20 GHz by employing time-interleaved optical sampling.