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.     

Simultaneous modulation and transmission of 10-Gb/s baseband and 60-GHz microwave signals in a radio-over-fiber system

A novel radio-over-fiber (ROF) scheme simultaneously to modulate and transmit 10-Gb/s baseband and 60-GHz microwave signals on a single wavelength using single-sideband (SSB) modulation technique is proposed and verified by simulation. The scheme is based on a Dual-Parallel Mach-Zehnder Modulator (DPMZM). The scheme can carry the microwave signals on either the upper sideband (USB) or the lower sideband (LSB) only and the baseband signals on the other sideband. The optical 60-GHz millimeter wave (mm-wave) carrier is generated by means of subcarrier-multiplexing (SCM) technique to carry 155-Mb/s baseband signals while 10-Gb/s baseband signals are imposed on the original optical carrier via SSB modulation. The signals with dual services are successfully transmitted over 50-km single-mode fiber.     

Full-duplex transmission of IEEE 802.11ac-compliant MIMO WLAN signals over a 2-km 7-core fiber

In this Letter, we experimentally demonstrate a full-duplex transmission system of IEEE 802.11ac-compliant multiple-input multiple-output(MIMO) signals over a 2-km 7-core fiber for in-building wireless local-area network(WLAN) distributed antenna systems. For full-duplex 3 × 3 MIMO demonstration, the crosstalk impacts of both fiber-transmission-only and optic-wireless transmission situation are evaluated. The results indicate that the impact of crosstalk on radio-over-fiber(ROF) link performance is not significant and the quality of the cascaded multi-core fiber and wireless channel is mainly determined by the wireless part. To further improve the system capacity, polarization multiplexing(PolMux) technology is employed to achieve a full-duplex 6 × 6MIMO over a single 7-core fiber. Although employing the PolMux method will slightly decrease the EVM and condition number performance as opposed to a non-PolMux MCF system, it is still a competitive solution in large optical connection demand scenarios that require a low cost.     

Experimental demonstration on 40 Gbit/s all-optical multicasting logic XOR gate for NRZ-DPSK signals using four-wave mixing in highly nonlinear fiber

We propose and demonstrate all-optical multicasting logic XOR gate for non-return-to-zero differential phase-shift keying (NRZ-DPSK) signals by using non-degenerate four-wave mixing (FWM) in a highly nonlinear fiber (HNLF). Theoretical analysis regarding the operation principle of NRZ-DPSK logic XOR gate is clearly described by deriving an analytical solution under the non-depletion approximation. The NRZ-DPSK logic XOR operation is attributed to the linear relationship of complex amplitudes between converted idlers and input NRZ-DPSK signals. By using three non-degenerate FWM processes in an HNLF, 40 Gbit/s all-optical multicasting logic XOR gate for NRZ-DPSK signals are successfully demonstrated in the experiment.     

Study on compensating methods of transmission system at 40 Gb/s in photonic crystal fiber

<正>Two compensating methods about solitons transmition systems at 40 Gb/s in a photonic crystal fiber are investigated.The maximum transmission distance of the system is calculated numerically by sliding filters and synchronic modulation technology.The maximum transmission distance increases evidently which occasionally is three times longer than before.The results show that the actions of high order dispersion,polarization mode dispersion,and high order nonlinearity are weakened by the two methods. The compensating effect of synchronic modulation technology is better than that of the other one.The capability of the compensated system is ameliorated,which is shown by eye patterns.     

Performance evaluation of 100 and 200-Gb/s WDM PM-QPSK transmission systems: tolerance analysis to the optical link impairments according to the optical carrier shape

Polarization-multiplexing quadrature phase shift keying (PM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of the system using these formats varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper, we analyse the tolerance of PM-QPSK to linear and nonlinear optical impairments, including amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fibre Kerr nonlinearities. The simulation results show that RZ formats with a low-duty cycle have a higher tolerance to CD, PMD and intrachannel nonlinearities due to the reduction of pulse-to-pulse interaction. Conversely, the PM–NRZ-QPSK format has a higher spectral efficiency (SE) than other options and shows better tolerance to filtering distortion and CD in filterless networks.     

Monolithic integration of electroabsorption modulator and DFB laser for 10-Gb/s transmission

A strained InGaAsP-InP multiple-quantum-well DFB laser monolithically integrated with electroabsorption modulator by ultra-low-pressure (22 mbar) selective-area-growth is presented. The integrated chip exhibits superior characteristics, such as low threshold current of 19 mA, single-mode operation around 1550 nm range with side-mode suppression ratio over 40 dB, and larger than 16 dB extinction ratio when coupled into a single-mode fiber. More than 10 GHz modulation bandwidth is also achieved. After packaged in a compact module, the device successfully performs 10-Gb/s NRZ transmission experiments through 53.3 km of standard fiber with 8.7 dB dynamic extinction ratio. A receiver sensitivity of −18.9 dBm at bit-error-rate of 10⁻¹⁰ is confirmed.     

All-optical polarization-mode dispersion monitor for return-to-zero optical signals at 40 Gbits/s and beyond

The operation of a polarization-mode dispersion monitor insensitive to chromatic dispersion is demonstrated at 40 Gbits/s. The high-speed processing device is based on the Kerr effect and provides an optical power output as a reading of differential group delay. The monitor is compatible with return-to-zero modulation formats at data rates in excess of 40 Gbits/s and does not require the use of high-data-rate electronics.     

Theoretical analysis and experimental verification of a cost-effective chromatic dispersion monitoring method in a 40-Gb/s optical fiber communication system

A cost-effective technique for in-service chromatic dispersion monitoring in a 40-Gb/s optical communication system is proposed. Microwave devices are adopted to detect the electrical power of a specific frequency band. A simplified theoretical model is proposed and discussed focusing on the relationship between electrical power and chromatic dispersion at different frequency bands. The dynamic monitoring of chromatic dispersion is achieved using devices such as PIN detector, microwave amplifier, narrow-band microwave filter, and electrical power detector. The maximum detectable chromatic dispersion is 130 ps/nm and a resolution of 5.2 ps/nm/dB has been achieved in the frequency band centered at 12 GHz.     

Experimental demonstration of polarization multiplexing for simultaneously providing broadband wireless and wired access

A fiber-based wavelength-division-multiplexing (WDM) network utilizing polarization multiplexing (PolMUX) is proposed to simultaneously provide broadband wireless and wired services. In such a dual-service access network, the wireless and wired services are separately delivered in two orthogonal states of polarization with well independence in a single WDM channel. The impact of several polarization-dependent interferences becomes insignificant due to the relatively short transmission distance in access networks. The feasibility of PolMUX is experimentally demonstrated with a power penalty at BER = 10^-9 of about 0.5 dB and 1 dB for 2.5 Gb/s wired and wireless downstream services, respectively. The proposed system is compatible with the current reported techniques in either WDM passive optical networks (WDM-PON) or radio-over-fiber (ROF) systems.     

Experimental demonstration of 60 Gb/s optical OFDM transmissions at 1550 nm over 100 m OM1 MMF IMDD system with central launching

Record-high 60 Gb/s optical orthogonal frequency division multiplexing(OFDM) transmissions over intensity modulation and direct-detection(IMDD)-based 100 m optical mode(OM1) multi-mode fiber(MMF) links are experimentally demonstrated, utilizing 10 GHz electro-absorption modulated laser intensity modulators at a single 1550 nm wavelength. Adaptive bit loading and a simple central launching scheme of the proposed scheme show an effective way for combating the channel fading and simplifying the system structure. It shows good potential in short reach data center interconnections.     

Experimental demonstration of optical MIMO transmission for SCFDM-PON based on polarization interleaving and direct detection

The OFDM-PON and SCFDM-PON based on powerful digital signal processing (DSP) are promising candidates for next-generation optical access networks. Recently polarization-division-multiplexing (PDM) transmission with direct detection has been proposed for OFDM-PON to effectively reduce the bandwidth requirement of optical and electrical components. However, the PDM scheme has high algorithm complexity. In this paper, we propose a polarization interleaving (PI) approach, which can significantly reduce the bandwidth requirement for components while achieving a similar 2×2 MIMO algorithm with coherently-detected PDM-OFDM scheme. Downstream PI-SCFDM transmission is experimentally demonstrated. The scheme can be easily extended to OFDM-PON.     

Impact of optical modulation formats on SPM-limited fiber transmission in 10 and 40 Gb/s optimum dispersion-managed lightwave systems

In this paper, 10 and 40 Gb/s optical systems have been investigated for nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero (CSRZ) and RZ-differential phase-shift-keying (RZ-DPSK) data formats. For the range of the optical signal power from −5 to 15 dBm, a maximum self-phase modulation (SPM)-limited transmission distance L_SPM is determined with eye-opening penalty (EOP) >1 dB .The observations are based on the modeling and numerical simulation of optimum dispersion-managed transmission link. Transmission over distances of the order of several hundreds of kilometers has been shown with and without amplified spontaneous emission (ASE) noise of the in-line erbium-doped fiber amplifiers (EDFAs).     

Nonlinear polarization rotation in a dispersion-flattened photonic-crystal fiber for ultrawideband (>100 nm) all-optical wavelength conversion of 10 Gbit/s nonreturn-to-zero signals

We study the conversion bandwidth of the cross-polarization-modulation (XPoIM)-based wavelength conversion scheme with a dispersion-flattened highly nonlinear photonic-crystal fiber for signals with a nonreturn-to-zero (NRZ) modulation format. Both theoretical and experimental results show that the conversion bandwidth can be extended to cover a very wide band, including S-, C-, and L-bands for 10 Gbit/s NRZ signals (a total bandwidth of 120 nm is experimentally demonstrated). We also study the theoretical bandwidth limit for 40 Gbit/s NRZ signals. A significant extension of the conversion bandwidth using the XPoIM approach compared with the four-wave mixing approach previously reported is demonstrated.     

Excitation of the 1s 2- and 1s 4-levels of neon and argon by He+-impact at energies between 100 keV and 1000 keV

The excitation of the 1s ₂- and 1s ₄-levels of neon and argon by He⁺-impact has been studied in the energy range of 100 keV to 1000 keV. The total emission cross sections for the 1s ₂ levels show pronounced maxima at about 350 keV impact energy, whereas the cross sections for the 1s ₄ levels increase with decreasing energy.     

Simple and flexible generation of vestigial side band modified duobinary return-to-zero signals at 10, 20 and 40 Gb/s

We propose and demonstrate a simple and flexible approach to generate vestigial side band modified duobinary return-to-zero (VSB MD-RZ) signals at 10-40 Gb/s, using a dual-drive Mach-Zehnder modulator and a detuned optical band-pass filter. The performance of the proposed VSB MD-RZ signal is investigated by comparing with double side band MD-RZ (DSB MD-RZ) and conventional VSB MD-RZ. Bit error ratio (BER) measurement at 10 Gb/s shows an error free operation for the generated signal. Good performance is further observed after 100 km of single-mode-fiber transmission at 40 Gb/s.     

Use of 1-m Bi2O3 nonlinear fiber for 160-Gbit/s optical time-division demultiplexing based on polarization rotation and a wavelength shift induced by cross-phase modulation

We present, for the first time to our knowledge, experimental results of the use of a 1-m-long Bi2O3-based nonlinear fiber (Bi-NLF) with a nonlinear parameter gamma of approximately 1100 W(-1) km(-l) within an all-fiber-based 160Gbit/s optical time-division multiplexing (OTDM) data demultiplexer. Our demultiplexing switch basically uses the principle of the Kerr shutter, and its switching performance is further enhanced by the additional use of the wavelength blueshift of data pulses, which is induced by cross-phase modulation from the control pulse's trailing edge. The OTDM demultiplexer, composed of the 1-m Bi-NLF, readily achieves error-free demultiplexing operation of all 16 channels.     

Experimental and theoretical studies of the 4s 2 n p 2 P sequence in neutral gallium

Using timeresolved laser spectroscopy lifetime values as well as hyperfine coupling constants have been determined for the 4s²np²P_3/2 (n=7–11) states in⁶⁹Ga and⁷¹Ga. Theoretical calculations of hyperfine structures based on manybody perturbation theory have been performed in the same sequence (n = 4–8) for both finestructure components. The theoretical values are compared with existing experimental data.     

Multi-parametric optimized design of FWM-based tunable all-optical wavelength converters for 40 Gbit/s ASK and DPSK signals

A full numerical optimization method for the design of FWM-based frequency converters for WDM systems is presented, taking into account specific system constraints set by the designer. The method is illustrated with the design of separate transparent frequency converters for 40 Gbit/s ASK and DPSK signals using Truewave fiber.     

Experimental observation of a 1.5 microm band wavelength conversion and logic NOT gate at 40 Gbit/s based on sum-frequency generation

We have experimentally verified a new idea for 40 Gbit/s wavelength conversion within the 1.5 microm band based on sum-frequency generation (SFG) in a periodically poled LiNbO3 waveguide. The spectrum and the temporal waveform of the output pump reveal that the input cw pump is converted to an optical pulse during SFG. Not only wavelength conversion but also a logic NOT gate at 40 Gbit/s are experimentally observed.