Experimental and theoretical analyses of RSOA-based colorless-ONUs with 4PAM signal in the up-link

A scheme that utilizes the 4-level pulse-amplitude-modulated (4PAM) signal as the re-modulated signal of colorless optical network units (ONUs) based on reflection semiconductor optical amplifiers (RSOAs) is proposed. The system with 10-Gb/s non-return-to-zero (NRZ) downstream and 5-Gb/s 4PAM upstream signals is theoretically analyzed and experimentally verified. Simulation and experimental results reveal that the 4PAM re-modulated signal yields better performance than the NRZ signal in the upstream. A receiver power penalty of 1.6 dB is also improved by the 4PAM signal at back-to-back (BtB) transmission, whereas another receiver power penalty of 1.5 dB improved after 30-km single mode fiber transmission, where 4PAM signals are used as upstream signal.     

All-optical wavelength conversion for 10-Gb/s NRZ payload and 2.5-Gb/s OFDM label in optical-packet-switched network

Simultaneous wavelength conversion based on four-wave mixing (FWM) for 10-Gb/s NRZ payload and 2.5-Gb/s OFDM label signals in optical switching network is experimentally demonstrated. The dual-pump scheme based on FWM in semiconductor optical amplifier (SOA) is employed and simultaneous wavelength conversion for optical packet with one optical payload of 10-Gb/s non-return-to-zero (NRZ) on-off keying (OOK) signals and one optical label of 2.5-Gb/s OFDM signals are realized. The bit-error-rate performance is evaluated for both payload and label after wavelength conversion.     

Transmission of 2.5 Gb/s WDM Channels Spaced at 5 GHz over 480 km of Single-Mode Fiber

We demonstrate the transmission of 2.5-Gb/s WDM signals spaced at 5 GHz over 480 km of single-mode fiber. The results indicate that it should be possible to transmit more than one thousand 2.5-Gb/s channels spaced at 5 GHz over long distance.     

A cost-effective structure of a centralized-light-source WDM-PON utilizing inverse-duobinary-RZ downstream and DPSK upstream

In this paper, we propose a new structure of a centralized-light-source wavelength division multiplexed passive optical network (WDM-PON) utilizing inverse-duobinary-return-to-zero (inverse-duobinary-RZ) downstream and DPSK upstream. It reuses downstream light for the upstream modulation, which retrenches lasers assembled at each optical network unit (ONU), and ultimately cuts down the cost of ONUs a great deal. Meanwhile, a 50-km-reach WDM-PON experiment with 10-Gb/s inverse-duobinary-RZ downstream and 6-Gb/s DPSK upstream is demonstrated here. It is revealed to be a novel cost-effective alternative for the next generation access network.     

Demonstration of single channel 160-Gb/s OTDM 100-km transmission system

A 16 × 10-Gb/s optical time-division-multiplexing (OTDM) 100-km transmission system with home-made multiplexer is demonstrated experimentally. A demultiplexer based on two cascaded electro-absorption modulator (EAM) and a clock recovery unit form a feedback loop. Error-free demultiplexing from 160-Gb/s to 10-Gb/s after over 100-km transmission is achieved. The power penalty is about 3.5 dB with the bit error rate of 10⁻⁹.     

Pattern dependency comparison of four different 40-Gb/s optical duobinary transmitters using low-bandwidth modulators

We investigate the pattern dependency of the 40-Gb/s optical duobinary signals generated by a 10-Gb/s-rated Mach-Zehnder modulator with four different configurations. These configurations correspond to all possible combinations of a 15-GHz-bandwidth low-pass filter and a 0.24-nm bandwidth optical filter used to shape up the duobinary signals. We compare through experiment the back-to-back sensitivities and transmission performances of the duobinary signals for pseudorandom bit sequence lengths of 2⁷-1 and 2³¹-1. The results show that the combination of the 10-Gb/s-rated modulator and the 0.24-nm optical filter exhibits the best performance in terms of both the receiver sensitivity and pattern dependency owing to the good frequency response of the optical filter.     

Collective reception of orthogonal band multiplexed data streams for OFDM-PON upstream transmissions

We propose and demonstrate a novel OFDM-PON upstream transmission architecture with traffic aggregation by orthogonal band multiplexing. The aggregated data streams that propagate in different fiber lengths from ONUs are collectively received and demodulated using one receiver, when the OFDM signals are in a synchronous state. In simulation, four optical network units (ONUs) transmit upstream data at four different frequency bands, and use orthogonal band multiplexing with a proper configuration. The orthogonal band multiplexed 10-Gb/s OFDM signal is collectively received to validate the feasibility of the architecture. We also conduct a proof-of-concept experiment to verify the orthogonal band multiplexing and collective reception. We also verify that the tolerance to the time mismatch of the orthogonal band multiplexing is twice of the CP length.     

Performance of directly modulated OFDM data over multimode fiber link

The performance of orthogonal-frequency-division-multiplexing (OFDM) technology in the multimode fiber (MMF) optical communication system is investigated numerically. The mode dispersion in MMF is analyzed by utilizing the optical angular spectrum analysis method. Simulation results in terms of bit-error-rate (BER) and signal-to-noise ratio (SNR) show that the transmission distance can reach up to 2.5-km at 10^− 3 BER for 40-Gb/s data. Results of different modulation formats further indicate that better performance can be achieved by adopting multi-level modulation format.     

Gigabit-converged wired and wireless networks for simultaneous multi-services transmission

A novel architecture of converged radio-over-fiber(RoF) and wavelength division multiplexed passive optical network(WDM-PON) system,namely RoF-WDM-PON,is demonstrated.20-GHz 1-Gb/s radio frequency(RF) signals and 1-Gb/s baseband(BB) signals are simultaneously generated and transmitted using optical carrier suppression(OCS) modulation techniques.The proposed scheme is compatible with the conventional RoF and PON system.25-km single-mode fiber(SMF) transmission is successfully achieved.     

Novel orthogonal modulation format DRZ-FSK/DPSK for high-speed long-haul optical communication

We propose a novel advanced orthogonal modulation format dark return-to-zero frequency shift keying/differential phase shift keying （DRZ-FSK/DPSK） and its realization scheme. The DRZ-FSK/DPSK is generated by the combination of a 40-Gb/s return-to-zero （RZ） signal and a DRZ signal which is converted from the RZ using a semiconductor optical amplifier （SOA） based on nonlinear cross polarization rotation （XPR） and then re-modulated by high-bit-rate DPSK at 40 Gb/s. The feasibility of the scheme is exper-imentally demonstrated. Bit error rate （BER） results of the total 80-Gb/s DRZ-FSK/DPSK orthogonal modulation signal with a subsequent 100-km single-mode fiber （SMF） transmission link show its potential for future high-speed long-haul optical communication.     

Investigation of a high-speed optical FSK scheme for WDM-PON applications with centralized lightwave source

This paper proposes and numerically investigates a novel high-speed wavelength-division-multiplexed passive optical network (WDM-PON) architecture with colorless user terminals based on the use of orthogonal modulation scheme for downstream and upstream transmission. The 40 Gb/s optical frequency shift keyed (FSK) downstream data is generated based on carrier-suppressed modulation. At optical network unit, the downstream signal is directly re-modulated by the 2.5 Gb/s up-stream data and sent back with the same fiber. Error free transmission over 20 km single mode fiber can be observed for both downstream and upstream signals in our simulation. Power budget, tolerance of channel spacing, FSK tone spacing and dispersion are all investigated. Factors that might influence the stability of the system are analyzed and an extended hybrid wired/wireless version of the scheme is also given.     

10 Gb/s TDM passive optical networks using four wavelengths multiplexed channels

We propose a new architecture for 10 Gb/s upstream traffic in TDM-PON using externally injection-locked Fabry-Perot laser diodes (FP-LDs) in each optical network unit (ONU). Four directly modulated 2.5 Gb/s FP-LDs were injection-locked by continuous wave (CW) carriers distributed from the optical line terminal (OLT). Hence, a total of 10 Gb/s upstream traffic can be achieved. Experimental results show negligible power penalty at a transmission of 25 km standard single mode fiber (SMF) without dispersion compensation. The performance of the injection-locked FP-LD is also studied.     

Label swapping and packet transmission of DPSK-labeled PPM signal in optical label switching

A label swapping scheme of an optical labeled signal with differential phase shift keying(DPSK) for label at 2.5 Gb/s and pulse position modulation(PPM) for payload at 40 Gb/s is demonstrated by simulation.Power penalties of ～1.8 and ～0.8 dB are achieved for both the payload and label over 80-km single mode fiber(SMF) transmission.This labeling scheme allows the use of four-wave mixing(FWM) in semiconductor optical amplifier(SOA) to perform label erasure,with advantages of transparence for bit rate,high processing rate,simple architecture,and low cost.Label swapping is demonstrated with appropriate penalties of-3.5 and 0.8 dB for PPM payload and new DPSK label,respectively.To further prove the effectiveness of the proposed scheme,label swapping in the case of using 10-Gb/s DPSK label is also investigated with the power penalties of 6 and 2 dB for PPM payload and new DPSK label.     

Stable error-free single channel 160-Gb/s OTDM 100-km transmission via high-precision dispersion management

<正>A single channel with a 160-Gb/s optical time-division-multiplexing(OTDM) transmission over 100 km is fabricated.With the help of 500-GHz optical sampling oscilloscopes,the fiber length is adjusted to the order of 10 m,which corresponds to the accuracy of 0.4 ps for the dispersion compensation.The dispersion map is optimized for the 100-km transmission link.A completely error-free transmission with the power penalty of 3.6 dB is achieved for 2 h without using forward error correction.     

Applications of optical duobinary in optical carrier suppression and separation labeling

A novel approach is used to implement optical carrier suppression and separation （OCSS） labeling. Then, the performance of 10/40-Gb/s duobinary payload with 2.5-Gb/s amplitude shift keying （ASK） or duobi- nary label by numerical simulations is studied. Influencing factors, such as demultiplexer bandwidth and fiber Bragg grating （FBG） filter bandwidth, are investigated. Simulation result shows that the received sensitivity of ASK label is higher than that of the duobinary label, while the received sensitivity of duobi- nary payload with duobinary label is higher than that with ASK label.     

Novel WDM-PON architecture for simultaneous transmission of unicast data and multicast services

We propose a novel wavelength-division multiplexed passive optical network （WDM-PON） to simultaneously transmit unicast data and multicast services with upstream data re-modulation in optical network units （ONUs）. For each wavelength channel in the optical line terminal （OLT）, the downstream unicast data are applied to one arm of a dual-parallel Mach-Zehnder modulator （DPMZM） to generate baseband unicast non-return-to-zero （NRZ） signal. A radio frequency （RF） control signal is applied to the other arm to present two un-modulated sidebands for multicast data modulation in a differential phase-shift keying （DPSK） format. The flexible and dynamic multicast services are realized by simply switching the RF control signal on or off. The proposed scheme is experimentally demonstrated with 1.25-Gb/s downstream unicast, multicast, and upstream data.     

All-optical up-conversion for 2.5-Gb/s signals in ROF systems based on FWM effect in HNLF

We propose and demonstrate experimentally a novel scheme to realize all-optical up-conversion and wavelength-conversion based on the bi-directional-pump four-wave mixing （FWM） effect in high nonlinear fibers （HNLFs）.The pump is generated with optical carrier suppression in a Mach-Zehnder modulator.The two pumps are always parallel and phase-locked.A balance-detection photo-detector for optical signal detection is employed with 3-dB improvement in power penalty.The 2.5-Gb/s signals are transmitted successfully over the 25-km single-mode fiber in 30-GHz radio over fiber （ROF） systems.     

SOA Direct Modulation in Wavelength-Selectable Laser Array Light Sources

We demonstrated, for the first time, 2.5-Gb/s SOA direct modulation in the wavelength-selectable DFB laser array. The SOA direct modulation was achieved in the wide tuning range of 22.7nm by selecting arrayed laser and tuning the temperature. 40-km transmission was also confirmed..     

WDM-PON upstream transmission using Fabry–Perot laser diodes externally injected by polarization-insensitive spectrum-sliced supercontinuum pulses

We propose, a novel upstream transmission scheme for high speed wavelength division multiplexed passive optical networks. Upstream transmission at bit rate of 2.5 Gb/s was demonstrated using a Fabry–Perot (FP) laser diode (LD) externally injected by a spectrum-sliced polarization-insensitive supercontinuum pulse source, located at central office. The impact of Rayleigh backscattering on transmission performance is also investigated. The proposed scheme is expected to be cost-effective since low-cost FP LDs are used for light sources.     

Directly Modulated 10 Gb/s Signal Transmission over 320 km of Negative Dispersion Fiber for Regional Metro Network

We demonstrate the transmission of directly modulated 10-Gb/s WDM signals over 320 km of negative dispersion fiber (dispersion:-2.5 ps/km/nm @1550 nm) without dispersion compensation. The results indicate that a regional metro WDM network could be implemented cost-effectively by using the proposed negative dispersion fiber and direct modulated lasers.