Kun-Chieh Yu

10 Gbit/s all-optical non-return to zero-return-to-zero data format conversion based on a backward dark-optical-comb injected semiconductor optical amplifier

By using a semiconductor optical amplifier backward injected by a dark-optical-comb pulse train at 10 GHz, we demonstrate a 10 Gbit/s all-optical nonreturn-to-zero (NRZ) to return-to-zero (RZ) format conversion of an incoming optical pseudorandom binary sequence (PRBS) data stream. Both the polarity and the wavelength of data are conserved during format conversion. Without any pre-amplification, the extinction ratio of degraded optical NRZ PRBS data is greatly improved from 7.13 to 13.6 dB after NRZ-to-RZ conversion. An ultralow bit-error rate of 10(-12) at a data rate as high as 10 Gbits/s is obtained with a received optical power of -18.3 dBm. The converted RZ PRBS data exhibit a negative power penalty of >3.7 dB compared with the NRZ PRBS data at a bit-error rate of 10(-12).

All-Optical Decision-Gating of 10-Gb/s RZ Data in a Semiconductor Optical Amplifier Temporally Gain-Shaped With Dark-Optical-Comb

We demonstrate a novel all-optical noninverted OC-192 return-to-zero (RZ) decision-gate by using a semiconductor optical amplifier (SOA) which is gain-controlled to achieve an extremely high cross-gain-modulation depth and a narrow gain window. A dark-optical-comb generated by reshaping the optical clock RZ data in a Mach-Zehnder intensity modulator is employed as an injecting source to temporally deplete most of the gain in the SOA. Such a dark-optical-comb injected SOA decision-gate exhibits improved 3R regeneration performances such as a timing tolerance of 33.5 ps, Q -factor of 8.1, an input dynamical tolerance of 14 dB, and an extinction ratio (ER) of 14 dB. The deviation between the wavelengths of backward injected dark-optical-comb and input RZ data for optimizing the ER of the decision-gate is determined as Deltalambda=19 nm. Under a threshold operating dark-optical-comb power of 7 dBm, such a decision-gate can recover the -18.5-dBm degraded RZ data with a bit-error-rate of less than at 10-9 Gb/s. A negative power penalty of -4.2 dB is demonstrated for the RZ data after 50-km propagation and decision gating.

Dynamic chirp control of all-optical format-converted pulsed data from a multi-wavelength inverse-optical-comb injected semiconductor optical amplifier

By spectrally and temporally reshaping the gain-window of a traveling-wave semiconductor optical amplifier (TWSOA) with a backward injected multi- or single-wavelength inverse-optical-comb, we theoretically and experimentally investigate the dynamic frequency chirp of the all-optical 10GBit/s Return-to-Zero (RZ) data-stream format-converted from the TWSOA under strong cross-gain depletion scheme. The multi-wavelength inverse-optical-comb injection effectively depletes the TWSOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 6.7 GHz. Even at high inverse-optical-comb injection power and highly biased current condition for improving the operational bit-rate, the chirp of the multi-wavelength-injection converted RZ pulse is still 2.1-GHz smaller than that obtained by using single-wavelength injection at a cost of slight pulse-width broadening by 1 ps.

10 Gbit/s all-optical NRZ-to-RZ data format in a dark-optical-comb injected semiconductor optical amplifier

All-optical 10 Gbit/s NRZ-to-RZ data-format conversion in a backward dark-optical-comb injected semiconductor optical amplifier with BER of 10-13 at receiving power of -19 dBm and a positive power penalty of 3.7 dB is primarily demonstrated

All-optical pulse data generation in a semiconductor optical amplifier gain controlled by a reshaped optical clock injection

Wavelength-maintained all-optical pulse data pattern transformation based on a modified cross-gain-modulation architecture in a strongly gain-depleted semiconductor optical amplifier (SOA) is investigated. Under a backward dark-optical-comb injection with 70% duty-cycle reshaping from the received data clock at 10GHz, the incoming optical data stream is transformed into a pulse data stream with duty cycle, rms timing jitter, and conversion gain of 15%, 4ps, and 3dB, respectively. The high-pass filtering effect of the gain-saturated SOA greatly improves the extinction ratio of data stream by 8dB and reduces its bit error rate to 10−12 at −18dBm.

Optimizing the Extinction Ratio and Error Bit Penalty of the On-Off-Keying Pulse Data With Gain-Constrictive SOA

On/off extinction ratio and receiving power penalties of a 10-Gb/s all-optical on-off-keying pulse data generated from a multiwavelength dark-optical-comb injected semiconductor optical amplifier (SOA) is analyzed. Such an SOA with a temporally constricted gain window is employed to offer an on-off-keying (OOK)-generated data stream with on/off extinction ratio of 17 dB and bit error rate (BER) of 10-13 at a receiving optical power of -18 dBm. With an input nonreturn-to-zero (NRZ) power as low as - 15 dBm and an injected dark-optical-comb power of 16.5 dBm, the generated OOK pulse data reaches a BER 10-13 at receiving power as low as -18.5 dBm. The OOK operation in the SOA also exhibits a decision-gate function with improved negative power penalty of 1.5 dB as compared with the back-to-back NRZ transmission condition. The injection via a multiwavelength dark-optical-comb source further benefits from a lower noise level as compared with single-wavelength laser or broadband spontaneous emission source. Such a system exhibits a tolerance for detuning timing of > 65% period with power penalties on the on/off extinction ratio and the receiving power of 3 and 1 dB, respectively. Even after 25-km propagation in a single-mode fiber spool, there is only a power penalty of 0.5 dB at a BER of 10-13 obtained for the generated pulse data stream.

All-Optical RZ Data Conversion With Temporally and Spectrally Gain-Sliced Semiconductor Optical Amplifier Via Broadband Optical Injection

We investigate the effect of the backward injecting linewidth on the rise/fall time, duty cycle, and frequency chirp of the 10 Gb/s format-converted pulsed return-to-zero (RZ) data stream from the traveling-wave semiconductor optical amplifier (TWSOA) with its gain profile temporally and spectrally reshaping by a backward injected single- or multimode inverse-optical-comb. The rising time remains almost unchanged; however, the falling time was monotonically reduced by increasing injection power. The evolution of full-width at half-maximum with injection power exhibits similar trend with falling time. In comparison with single-mode inverse-optical-comb injection, the multimode injection exhibits frequency-chirp reduction and better on/off extinction performances. Under the injection of multi- and single-mode inverse-optical-combs into the TWSOA at extremely high gain condition, the multi- and single-mode injection converted pulsed RZ data pulsewidths are 32 and 31 ps with corresponding peak-to-peak chirps of 10 and 12 GHz, respectively. The chirp can abruptly be reduced to 1.2 GHz by reducing the TWSOA biased current to 100 mA.

Extraordinary light absorptance in graphene superlattices

Extraordinary absorption decrease in graphene superlattices in the visible range is presented. Due to competition between loss and resonant reflection at resonance, the absorption displays non-monotonic behavior. As the period number increases above a certain critical value, absorption decreases with the increase in the period number. This is in contrast to ordinary absorption for a non-resonant condition, which monotonically increases with the period number. Moreover, this extraordinary property can also be controlled by applying a gate voltage to graphene sheets. The results provide not only a new understanding of graphene physics but also an application in nanophotonics and optoelectronics.

Chirp control of 10 Gbit/s RZ data stream converted by semiconductor optical amplifier using multi-mode inverse optical comb injection

Comparison on shortened falling-time, reduced chirp and improved on/off extinction ratio of 10 Gbit/s all-optical pulsed RZ generation in single-and multi-wavelength inverse-optical-comb injected semiconductor optical amplifiers with temporally reshaped gain-window is demonstrated.

Duty-Cycle and Chirp Diagnosis of All-Optical Format Conversion Data in Multi- and Single-Wavelength Inverse Optical Comb Injected Semiconductor Optical Amplifier

Comparison on shortened falling-time, reduced chirp and improved on/off extinction ratio of 10 Gbit/s all-optical data-format converted pulse-stream in single- and multi-wavelength inverse-optical-comb injected semiconductor optical amplifiers with temporally reshaped gain-window is demonstrated.