We present results from theoretical analysis of the phase dynamics in semiconductor optical amplifiers(SOAs).In particular,we focus on an aspect of the ultra-fast phase recovery that currently does not have adequate in-depth theoretical analysis and clear explanation of the physical mechanism.We build up a numerical model to analyze the ultra-fast phase recovery of semiconductor optical amplifiers in details.To investigate the phase response characteristics,we analyze the different contributions to the phase shift,including intra-band effects such as carrier heating,spectral hole burning,and inter-band effects such as carrier depletion.In addition,the impact of the pulses energy on phase shift is also investigated.Based on the analysis of phase response characteristics,we further explain the reason why a delay occurs between gain response and phase response.The analysis results are in good agreement with the reported experimental results.The results presented in this paper are useful for the SOA-based ultra-fast optical signal processing,such as optical switches,optical logic gates,and optical Add/Drop multiplexer.
A new radio-over-fiber system for use in hybrid fiber-wireless access networks is proposed and experimentally demonstrated,which is based on cascaded injection-locked Fabry-Perot laser diodes.It is verified that the proposed technique is able to achieve a good suppression ratio of an optical carrier suppressed(OCS) signal simultaneously through a programmable optical filter and by use of optical injection locking technique.A 60 GHz carrier with downlink baseband data has been generated and down converted to baseband signal in order to be characterized in our laboratory.
We propose and experimentally demonstrate mutual optical format conversion between signals characterized as 10-Gb/s nonreturn-to-zero on-of-keying(NRZ-OOK)and NRZ binary phase-shift keying(BPSK)types.The conversion is based on stimulated Brillouin scattering(SBS)in a single-mode optical fber.An OOK signal is converted into a BPSK signal through optical carrier absorption,for which a SBS loss of30 MHz is used in long-haul transmission.The converted BPSK signal is reverted to an OOK signal with a corresponding SBS gain of 30 MHz for direct detection.The proposed OOK-to-BPSK and BPSK-to-OOK format conversions can be implemented in transmitter and receiver nodes by using a laser source as the Brillouin pump.
We propose a scheme for mitigating Rayleigh backscattering noise and demodulating differential phaseshift keying (DPSK) signals in wavelength-division-multiplexed passive optical networks (WDM-PONs) with injection-locked Fabry-Perot laser diodes (FP-LDs). Signal demodulation and wavelength conversion are simultaneously realized on the basis of the frequency deviation and red shift of longitude modes in the FP-LDs. Experimental results demonstrate that the demodulation and wavelength conversion of 2.5-Gb/s DPSK signals are achieved. A power penalty of about 1.6 dB at a bit error rate of 10 9 is measured after transmission over 25-km single mode fiber.
In this paper, key technologies, system proposals and future directions of next generation passive optical networks stage 2 （NG-PON2） are reviewed. We first discuss the potential solutions for NG-PON2 standardiza- tion. Then we focus on time and wavelength division multiplexed PON （TWDM-PON）, which is the primary solution selected by Full Service Access Network （FSAN）. The key technologies in TWDM-PON configuration are analyzed, including how to improve the bandwidth capacity and power budget of the system, and choose upstream tunable transceiver, etc. Several system proposals are illustrated as candidates for NG-PON2 configuration.
We propose a new method for characterizing optical phase modulators based on phase modulation-to-intensity modulation (PM-to-IM) conversion in dispersive fibers.The fiber dispersion spectrally alters the relative phasing of the phase-modulated signal and leads to the PM-to-IM conversion,which is extended to measure the modulation efficiency of optical phase modulators.In the demonstration,the frequency-dependent modulation index and half-wave voltage are experimentally measured for a commercial phase modulator.Compared with conventional methods,the proposed method works without the restriction of small-signal operations,and allows swept-frequency measurement with high resolution and accuracy by using a vector network analyzer.
In this letter, two kinds of continuous wavelength-tunable light sources are achieved and investigated experimentally using a self-seeding reflective semiconductor optical amplifier (RSOA). Over 40 single mode wavelengths with 100 GHz spacing are generated by setting the parameters of the wavelength selective switch. The peak power of each wavelength reaches over 0.2 dBm with the signal-to-noise ratio (SNR) > 35 dB. The proposed schemes are appropriate for multi-wavelength-tunable light sources; the maximum number of wavelengths generated can reach to 4.
