Lilin Yi

Optical millimeter-wave generation or up-conversion using external modulators

We have experimentally compared the performances of optical millimeter-wave generation or up-conversion using external modulators based on different modulation schemes. The generated or up-converted optical millimeter wave using the optical carrier suppression (OCS) modulation scheme shows the highest receiver sensitivity, highest spectral efficiency, and smallest power penalty over long-distance delivery. Moreover, the OCS modulation scheme has a simple configuration and low-frequency bandwidth requirement for both electrical and optical components. Employing an OCS modulation scheme, 16-channel dense wavelength-division multiplexing signals at 2.5-Gb/s per channel have been up-converted to a 40-GHz carrier simultaneously.

Symmetric 40-Gb/s TWDM-PON With 39-dB Power Budget

Time- and wavelength-division multiplexed passive optical network (TWDM-PON) has been selected by full service access networks as a primary solution for next generation PON stage 2 in April 2012. In this letter, we propose and demonstrate a symmetric 40-Gb/s TWDM-PON with 39-dB power budget. A reflective semiconductor optical amplifier is used in optical network unit as a pre-amplifier to enhance the sensitivity of downstream signals. For the upstream direction, a thermally-tuned directly modulated laser with 10-Gb/s modulation rate is used as upstream colorless source, and a chirp management filter is employed in optical line terminal to mitigate chromatic dispersion therefore enabling fiber transmission. Symmetric 40-Gb/s TWDM-PON is experimentally demonstrated with a power budget of 39 dB, which could support 25-km fiber transmission and 1:1000 splitting ratio.

All-Optical Format Conversion From NRZ to BPSK Using a Single Saturated SOA

All-optical format conversion from nonreturn-to-zero (NRZ) to binary phase-shift keying format is experimentally demonstrated at 8 Gb/s using a single semiconductor optical amplifier (SOA). The conversion is based on the gain and phase modulations of the SOA on an input NRZ signal of finite extinction ratio

Delay of Broadband Signals Using Slow Light in Stimulated Brillouin Scattering With Phase-Modulated Pump

Slow light due to stimulated Brillouin scattering in fibers is a promising technique to realize all-optical data storage and synchronization. For delaying high-speed data, we demonstrate an approach to solve the problem of narrowband Brillouin gain by phase-modulating the Brillouin pump. The bit rate of the phase-modulating signal determines the Brillouin gain bandwidth. A 1.25-Gb/s nonreturn-to-zero pseudorandom binary sequence data is delayed by 520 ps with a phase-modulated pump operating at 2.5-Gb/s bit rate. We have also observed the pattern-dependent delay and distortion of the data caused by the filtering characteristics of Brillouin amplification, and we have suppressed the distortion by detuning the carrier of the signal away from the Brillouin gain peak

Improvement of gain and noise figure in double-pass L-band EDFA by incorporating a fiber Bragg grating

An obvious improvement on both the gain and noise figure (NF) is demonstrated in the new double-pass L-band erbium-doped fiber amplifier (EDFA) with incorporating a fiber Bragg grating (FBG). Compared with the conventional L-band EDFAs, the gain is improved by about 6 dB in the new configuration for a 1580-nm signal with an input power of -30 dBm at 60 mW of 980-nm pump power. It is important that the NF is greatly reduced in the new configuration, as the FBG greatly compresses the backward amplified spontaneous emission. For the economical utility of pump power and erbium-doped fiber length, such a configuration may be a very competitive candidate in the practical applications of L-band EDFAs.

Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber

We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber.

Compatible TDM/WDM PON Using a Single Tunable Optical Filter for Both Downstream Wavelength Selection and Upstream Wavelength Generation

We propose a hybrid time-division multiplexing/wavelength-division multiplexing passive optical network (TDM/WDM-PON) architecture compatible with the traditional TDM-PON configuration using a power splitter in the remote node. A tunable optical filter (TOF) is used to select the downstream wavelength in each optical network unit. Meanwhile, the TOF plays a second role of seeding a reflective semiconductor optical amplifier (RSOA) so as to construct a tunable fiber-ring laser as colorless upstream source. A stable performance is observed for the upstream laser source tuned from 1535 to 1565 nm and with a modulation data rate of 1.25 Gb/s. The upstream wavelength has a offset with the central wavelength of the TOF when the RSOA is biased at its saturation region, which mitigates the Rayleigh backscattering and back reflection-induced crosstalk in single-fiber bidirectional PON systems.

28 Gb/s duobinary signal transmission over 40 km based on 10 GHz DML and PIN for 100 Gb/s PON

In this paper, we demonstrate the direct modulation and direct detection of 28-Gb/s duobinary signal for the future downstream capacity upgrade in next generation passive optical network (PON). Commercial 10-GHz directly modulated laser (DML) and PIN with a combined modulation bandwidth of ~7 GHz are used as transmitter and receiver respectively. In order to mitigate the chromatic dispersion induced signal distortion, an optical delay interferometer (DI) is employed to narrow down the signal spectrum, thereby realizing 40-km single mode fiber (SMF) transmission in C-band. Besides, the chirp-induced spectral broadening of the directly modulated signal enables a higher launch power than external modulation schemes, which increases the loss budget of the system. As a result, 31-dB loss budget is achieved, supporting 64 users with 40-km reach. Also, as the transceivers in both optical line terminal (OLT) and optical network unit (ONU) are commercial l0-GHz devices, the proposed scheme is compatible with 40-Gb/s time and wavelength division multiplexing passive optical network (TWDM-PON) systems, providing a cost-efficient alternative for the development of 100G PON.

Design and System Demonstration of a Tunable Slow-Light Delay Line Based on Fiber Parametric Process

We design a tunable slow-light delay line based on fiber-optic parametric process by shaping the gain bandwidth, with its operating wavelength in the present telecommunication window. We derive an analytical expression for the time delay and perform simulations for the delay lines made of dispersion-shifted fiber (DSF) and nonzero dispersion-shifted fiber, respectively. We also experimentally demonstrate the system performance of slow light by propagating 10-Gb/s return-to-zero data packets through such a tunable delay line based on DSF

A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper

A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity.