We numerically investigate a transparent wavelength conversion for a high-speed orthogonal frequency-shift keying and
intensity-modulated (FSK/IM) modulation format based on four-wave-mixing (FWM) in semiconductor optical amplifier
(SOA). The inter-band and intra-band carrier dynamics, such as gain saturation, carrier density pulsation (CDP), carrier
heating (CH) and spectral hole burning (SHB) have all been taken into account in our in-house SOA model. Simulation
results show that about 3.5-dB and 1.5-dB power penalty at BER of 1e-9 can be achieved for the 40-Gb/s FSK payload and
2.5-Gb/s IM label after conversion. With fixed signal wavelength, the 1-dB sensitivity penalty range of the pump wavelength
for the payload and label can be observed at the value of 4-nm and 5.6-nm respectively. Additionally, the dynamic range of
IM modulation depth from 0.3 to 0.8 can also be observed after conversion.
All-optical wavelength conversion is considered to be a key technology in future high-speed large-capcity dense
wavelength-division-multiplexed (DWDM) optical networks. Transparent wavelength conversion is highly desired
especially for various advanced modulation formats. We report a novel 40 Gbit/s all-optical transparent frequency-shift
keying (FSK) wavelength conversion and logic NOT gate by exploiting cascaded second-harmonic generation and
difference-frequency generation (cSHG/DFG) in a periodically poled lithium niobate (PPLN) waveguide. In addition,
transparent wavelength conversions for optical duobinary (ODB) and alternate-mark inversion (AMI) modulation
formats are demonstrated in the experiment.
All-optical wavelength conversion of differential phase-shift keyed (DPSK) signals based on SOA in a Mach-Zehnder interferometer (SOA-MZI) configuration is simulated and analyzed using the transfer function of MZI and a wideband dynamic model of SOA. The operation principle is analyzed and operation point selection, influence of SOA physical parameters, different signal format and operation speed are discussed in detail.
The results of 10Gb/s operation show that SOA-MZI is compatible with both non-return-to-zero (NRZ) and return-to-zero (RZ) formatted signals. However, the conversion performance is sensitive to the operation point of the involved SOAs. To maximize the Q value of the demodulated conversion signal, the power and wavelength of the original DPSK signal and the probe light should be optimized to obtain approximately π phase difference between the upper and lower arms of MZI in the middle of each bit. Besides, SOA with short carrier lifetime and large linewidth enhancement factor is preferred for wavelength conversion applications. 40Gb/s operation is also simulated with SOA carrier lifetime of 100ps, and the results strongly suggests 40Gb/s operation with RZ formatted signals and relatively large input powers of the clock signal.
Based on a Mach-Zehnder interferometer and optical temporal time delay (OTDL), we propose and demonstrate
experimentally an all-optical 40-Gb/s RZ-DPSK to ASK-Manchester format conversion. This obtained ASK-Manchester
signals have the phase changes due to the demodulation of RZ-DPSK, which is called as phase-incorporated
ASK-Manchester signal. Compared with pure Manchester signal, the simulated results show that the phase-incorporated
ASK-Manchester signal has a compact optical spectrum and lower power at the low radio frequency (RF) frequencies, which
presents high tolerance on chromatic dispersion and little the cross-talk between payload and label. Moreover, the efficiency
and the BER performance of conversion and the dynamic range of fiber input power, transmission length, and chromatic
dispersion tolerance of the converted ASK-Manchester are detailed discussed. Less than 1-dB power penalty over 50-km
SMF transmission is observed.
This paper proposes and numerically investigated a novel high-speed wavelength-division-multiplexed passive optical
network (WDM-PON) architecture with colorless user terminals based on the use of a different modulation scheme for
downstream and upstream transmission. In the central office (CO), based on the carrier suppressing functionality of
Mach-Zehnder modulator (MZM) and differential-phase-shift-keying to amplitude-shift-keying conversion using
Mach-Zehnder delay interferometer, 40-Gb/s optical frequency shift keying (FSK) is generated and employed for
transmitting the downstream data. In the remote node (RN) or optical network unit (ONU), the upstream data is
re-modulated at 2.5-Gb/s by an intensity modulator and sent back to CO with the same fiber. Since only one light source
is needed for each WDM channel, and the MZM to generate carrier suppressed signal can be shared by all the channels, a
centralized 40-Gb/s WDM-PON access system with low-cost configuration is realized. Error free transmission over
20-km SMF can be observed for both downstream and upstream signals in our simulation.
We propose and demonstrate a novel orthogonal optical labeling scheme based on 40-Gbit/s optical frequency-shift keying (FSK) payload and 2.5-Gbit/s intensity-modulated (IM) labeling. Using the technology of carrier-suppressed modulation and conversion of differential phase-shift keying to IM, only one light source is needed to generate the optical FSK signal. The system performance, including range of IM modulation depth, bit error ratio, and dispersion limitation, is carefully investigated by numerical simulation. With IM modulation depth of 0.4, the 40 Gbit/s FSK payload and 2.5-Gb/s IM label are transmitted over a 50-km standard single mode fiber (SMF) with 0.87 and 0.92 dB penalty and show immunity to input power range upto 11 and 15 dB, respectively. Optimal methods to improve the system performance are also proposed and discussed. After optimization, the IM modulation depth can be reduced to 0.2.
In OBS network, one key factor is implementing a switching fabric to achieve low bursts loss rate as low as possible.
Another key factor in OBS network is scheduling bursts after switch fabric to an output port to achieve best utilizing
bandwidth. Until now the performance of switch fabric and scheduling algorithm is analyzed with a uniform assigned
traffic so called in this paper. The uniform assigned traffic is meant that the input traffic go to every output port with a
same probability of 1/N independently. Unfortunately, this uniform assigned traffic may not the most suitable way to
present the real world traffic. To deal with this problem, we present a new bursty assigned traffic model for analysis and
performance evaluation of OBS network. Like a legacy bursty traffic the bursty assigned traffic is divided to two cycle:
bursty cycle and nonbursty cycle. The input traffic is directed to an output port with a probability larger than 1/N in
bursty cycle and is directed to an output port with a probability less than 1/N or none in nonbursty cycle. Then making
use of the definition the bursts loss ratio of switch fabric and the LAUC-VF scheduling algorithm under uniform
assigned and bursty assigned traffic is presented and compared in the paper.
We propose a novel scheme of high bit rate optical frequency
shift-keying transmitter. Base on the periodic notch spectral
properties of Mach-Zehnder delay interferometer and the carrier suppressing functionality of Mach-Zehnder modulator, a
high-speed optical FSK signal can be simply generated with another phase modulator and a single wavelength laser source.
The transmission characteristics of this FSK signal are investigated under varying dispersion management. Simulated
results show that 40Gb/s FSK signal gives only 1dB penalty after 80 km SMF transmission link under the
post-compensation management scheme.
We experimentally demonstrate a novel decimal optical buffer scheme based on a multiloop configuration and a single switch element—an optical crosspoint switch (OXS) matrix. Its variable-delay range is of 1 to 999 times the basic delay unit. The buffer dynamic reconfiguration can be achieved at nanosecond switching speed. Our results show that by using a differential phase-shift keying (DPSK) payload in the buffer it can outperform an on-off keying payload with 4-dB sensitivity improvement owing to its alleviation of patterning-induced degradation, clearly validating DPSK as a promising modulation format to overcome nonlinear impairments and to extend number of hops in all-optical packet-switching network.
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