Xiuhua Yuan

Experimental demonstration of 40 Gbit/s hybrid optical code-division multiplexing/ wavelength-division multiplexing system

A 40 Gbit/s hybrid optical code-division multiplexing OCDM/ wavelength-division multiplexing WDM system is experimentally dem- onstrated and simultaneous multiwavelength optical encoding of a single supercontinuum source using superstructured fiber Bragg grating is achieved. The interchannel interference and noise of the OCDM/WDM system is suppressed apparently by incorporating a nonlinear amplifying loop mirror, both the sidelobe and the pedestal are reduced, the wave- form quality of decoded signal is improved, and the original 8.2 ps auto- correlation peak of decoded pulse is compressed to 4.8 ps.

Analysis of turbo-coded optical wireless communication system based on on-off keying, binary phase-shift keying, and binary pulse position modulation

Optical wireless communication systems usually adopt on-off keying (OOK), binary pulse position modulation (BPPM), and binary phase-shift keying (BPSK). In this work, the scheme of systems based on a turbo code of OOK, BPPM, and BPSK is proposed, and the three different iterated maximum a posteriori (MAP) algorithms of turbo code are deduced. To use the turbo code based on different modulated formats over optical wireless channels we deduce the formula of an atmospheric channel signal-to-noise ratio versus the atmospheric visibility. Simulations show that the turbo code based on BPSK is well suited for optical wireless communication systems.

Grating-based 40-Gbit/s optical code-division multiplexing system incorporating a nonlinear amplifying loop mirror

Abstract. A seven-chip, 280-Gchip/s OCDM system incorporating qua-ternary phase coding and decoding is experimentally demonstrated. Theencoder and decoder, consisting of superstructured fiber Bragg gratings,are fabricated using the equivalent-phase-shift method; only ordinaryphase masks and submicrometer precision in control are required. Inter-channel interference noise is also considered and evaluated; 40-Gbit/s2-channel multiplexing is demonstrated. In addition, a nonlinear ampli-fying loop mirror NALM within the receiver is introduced to improve thesystem performance under two-channel operation. Switching is obtainedfor peak signal power less than 10 mW. We show that the NALM can actas a nonlinear processing element capable of reducing both the pedestalassociated with conventional matched filtering and the width of the as-sociated code recognition pulse.

Fiber optic surface plasmon resonance sensors for imaging systems

A fiber optic imaging sensor is presented that utilizes surface plasmon resonance (SPR) excitation. The configuration of this sensor allows for remote sensing and multiplexing. The sensor is advantageous in that it eliminates the traditional bulk optic prism in favor of a relatively simple and inexpensive design. Two sensor configurations are presented; the principle of one is based on using optical interference, and that of the other is based on using the optical intensity as in traditional bulk-optic SPR imaging systems. Experimental measurements indicate that the fiber optic sensor based on optical interference is compact and immune to noise due to ambient light, and is more powerful and reliable than the common SPR imaging sensor based on optical intensity. Using fiber optics, the theory of SPR, and interference, a new SPR imaging sensor is achieved, which is better fitted to applications.

Analysis of optical wireless communication system based on a novel turbo code

Atmospheric optical wireless communication is a fading channel because of the effect of atmospheric attenuation. We introduce a novel turbo code named the two-fold turbo code scheme to provide high performance for optical wireless communication. To use the two-fold turbo code over optical wireless channels, first deduce the formula of atmospheric channel signal-noise-ratio versus atmospheric visibility, then analyze the coding and decoding principle of the two-fold turbo code. Simulations show that the proposed two-fold turbo code significantly improves the performance of the system compared to the common turbo code.

An optimized scheme for broadening optical spectrum of 40-GHz ultra-short optical pulse trains

Effective utilization of highly nonlinear fiber (HNLF) with relative large normal dispersion to further broaden optical spectrum of 40-GHz, 1.2-ps optical pulse train is investigated, in which an optimized scheme is presented. In the scheme, the pulse is launched into the HNLF of the first section to generate the spectrum broadened linearly up-chirped pulse, and recompressed after propagating through a suitable length of conventional single-mode fiber (SMF) of the second section for the pulse chirp being compensated. At last, the pulse travels through the second HNLF of the third section for further optical spectrum broadening. This new scheme applies the chirp pulse compensation technique and has scalability to the peak power of seed pulse. The experimental results show that ~1.7 nm increment of 3dB spectrum bandwidth is obtained when the new scheme is implemented given the same HNLF length and input seed pluses, and the coherence properties of the original pulses are maintained. This scheme provides a more effective means of pulse spectrum broadening in the HNLF when the peak power of seed pulse is confined by the EDFA output power and the high repetition rate of pulse laser.

Design of the optical system for FSO access

Free space optics (FSO) is attractive for the last mile communication in recent years for many combining advantages of fiber communication and other wireless technologies. FSO can provide high data rate with low power consumption, high immunity to interference, convenient deployment and flexibility. Optical system is an important section in the FSO transceiver terminal. In this paper the design of optical system based on a single Galileo telescope for both transmit and receive is proposed, and a polarization beam splitter is adopted to apart the receiving light from transmitting light. The configuration can avoid interference from the retroreflecting light of the ocular effectively. Some factors that affect the performance of the optical system are analyzed, such as the geometrical spreading loss and the loss increment according to pointing error and telescope maladjustment. Power budget shows that the system can satisfy the need of access for 1km in the light fog, and 2km in the thin fog.

Performance analysis of bandwidth limited coherent time spreading OCDMA system employing DPSK format and turbo code

Differential phase shift keying (DPSK) data format is employed to combat noise in the bandwidth limited coherent time spreading (TS) optical code division multiplexing access (OCDMA) system. In addition, the performance of DPSK-OCDMA system with turbo coding is analysed and simulated. Theoretical results show that performance degradation due to bandwidth limitation could be effectively restrained by the DPSK-OCDMA scheme, and further performance improvement could be achieved by incorporating turbo coding into OCDMA system. It is confirmed that the number of active users is increased from K = 11 to K = 25 in bandwidth limited OCDMA system by employing DPSK format and turbo code for a given BER of 10-6.

Performance analysis of phase-encoded OCDMA system using superstructured fiber Bragg gratings

Correlation characteristics for phase-coding scheme utilizing superstructured fiber Bragg grating (SSFBG) as encoder/decoder are evaluated. The impact of transmission impairments and the receivers bandwidth limitation in the coherent OCDMA system is investigated, and the performance improvement by using optical thresholding is also analyzed.

Investigation on electro-optic single-sideband modulation using period phase reversal electrode

A novel single-sideband (SSB) modulator using period phase reversal electrode and the theoretical analysis on the principle is proposed and presented. The results show that the SSB modulator can reach an optical sideband suppression ratio over 40dB in 60GHz radio-over-fiber (ROF) system, which successfully reduce the power penalty due to the chromatic dispersion.