XGM Effect Research Articles

A cascadable all-optical half-subtracter based on cross-modulation effects in a single highly nonlinear fiber (HNLF)

An all-optical half-subtracter is proposed based on harnessing of 3rd order (χ(3)) non-linear effects such as cross-gain modulation (XGM) and cross-phase modulation (XPM) inside a single highly non-linear finer (HNLF), which is capable of operating at 100 Gbps operating bit rate. The XGM effect occurrence in HNLF has been exploited for the implementation of both borrow logics \(\left( {A.\bar{B}\,\& \,\bar{A}.B} \right)\). Whereas, the difference output of proposed half-subtracter represented by \(A \oplus B\) logic is obtained from XPM process taking place on low-energy continuous-wave (CW) probe signal which is co-propagating with two high energy pump signals. The proposed half-subtracter can exhibit cascadability, owing to single wavelength centric nature of all the three logic functions generated such as \(A.\bar{B}\), \(\bar{A}.B\,\&\,A \oplus B\). The proposed half-subtracter functionality is verified through inspection of temporal waveforms and eye diagrams of achieved output logic functions. Further, dependence of output function’s Q-factor and Extinction Ratio (dB) values on following parameters: pump/data signal powers (PA\(\&\)PB), CW probe power (PCW) and choice of CW probe operating wavelength (λCW) is also investigated and discussed. In the final stages, an investigation has been carried out by implementing secondary logic functions \(\left( {\left( {A.\bar{B}} \right).\bar{C},\,\left( {\overline{{A.\bar{B}}} } \right).{\text{C}}\text{,}\,\left( {\bar{A}.B} \right).\bar{C},\,\left( {\overline{{\bar{A}.B}} } \right).C,\,\left( {\overline{A \oplus B} } \right).C\,\& \,\left( {A \oplus B} \right).\bar{C}} \right)\) to examine the cascade-ability characteristics of the proposed half-subtracter. It has been shown by calculating temporal waveforms and eye diagrams of secondary logic functions such as \(\left( {A.\bar{B}} \right).\bar{C},\,\left( {\overline{{A.\bar{B}}} } \right).{\text{C,}}\,\left( {\bar{A}.B} \right).\bar{C},\,\left( {\overline{{\bar{A}.B}} } \right).C, \left( {\overline{A \oplus B} } \right).C\,\& \,\left( {A \oplus B} \right).\bar{C}\) that proposed cross-modulation effects in HNLF based half-subtracter is indeed cascadable.

A Novel Thresholder Based on XGM Effect in a DFB Laser Combined With External Optical Filtering

A novel thresholder based on cross-gain modulation (XGM) effect in a distributed-feedback (DFB) semiconductor laser combined with offset optical filtering is proposed and demonstrated. To the best of our knowledge, this is the first XGM effect-based thresholder that is operated by optical injection of a DFB laser. In this scheme, a DFB laser without an isolator is the key component, which costs less than the nonlinear devices required in other schemes. The spectrum output from the DFB laser can be broadened after the pulses injected to the laser cavity, which is induced by the XGM effect. Only the correct codes that have enough peak power will be able to broaden the spectrum of the DFB laser, while the low-power noise cannot. By offset filtering the broadened parts of the optical spectrum, the correct optical pulse is acquired, while the undesired noise is diminished. In this scheme, an injection power of 7 dBm is enough to generate the XGM effect, which is much lower than most of the existing schemes. In addition, as the DFB laser is used as the pump laser as well as the nonlinear medium, this scheme is more compact and low cost compared with the schemes proposed before.

반사형 반도체 광 증폭기를 이용한 음계수를 가지는 광 마이크로파 노치 필터

We propose and experimentally demonstrate a photonic microwave notch filter with a negative coefficient. The negative coefficient is obtained by using cross gain modulation (XGM) in a reflective semiconductor optical amplifier (RSOA). When the RSOA is operated in saturated region, the signal carried on the pump wavelength is inversely copied to the probe wavelength by the XGM effect, showing a negative coefficient. Time delay between pump signal and probe signal is provided by single mode fiber (SMF) with wavelength dependent time delay. The proposed microwave notch filter shows notch dips of more than 35.1 dB and free spectral range (FSR) of about 380.6 MHz. 논문 14-39C-05-03 The Journal of Korea Information and Communications Society '14-05 Vol.39C No.05 http://dx.doi.org/10.7840/kics.2014.39C.5.418 418 ※ 본 연구는 산업통산자원부 산하 (재)충청지역사업평가원 융합전자기기 선도사업 신호처리융합기기 프로젝트의 지원을 받아 수행된 연구임. ※ 이 논문은 2013년도 정부(교육부)의 재원으로 한국연구재단의 지원을 받아 수행된 기초연구사업임(NRF-2009-0093828). First Author : School of Information and Communications, Gwangju Institute of Science and Technology, wbkwon@gist.ac.kr, 정회원 ° Corresponding Author : School of Information and Communications, Gwangju Institute of Science and Technology, csp@gist.ac.kr, 정회원 * 광주과학기술원 정보통신공학부, cyk@gist.ac.kr. 정회원 ** 목포대학교, srlee@mokpo.ac.kr. 종신회원 논문번호:KICS2014-02-030, Received Feburary 3, 2014; Revised April 17, 2014; Accepted April 17, 2014 논문 / 반사형 반도체 광 증폭기를 이용한 음계수를 가지는 광 마이크로파 노치 필터

A tunable photonic microwave notch filter with a negative coefficient using nonlinear behavior of a reflective semiconductor optical amplifier

ABSTRACTWe propose and experimentally demonstrate a simple tunable photonic microwave notch filter with positive and negative coefficients. The negative coefficient is obtained from a single input signal (positive coefficient) using cross gain modulation (XGM) in a reflective semiconductor optical amplifier (RSOA). When the RSOA is operated in the saturated region, the signal carried on the pump wavelength is inversely copied to the probe wavelength by the XGM effect, showing a negative coefficient. This probe wavelength is easily generated by self‐injection locking the RSOA through a wavelength‐selective filter. Further, variable time delay for filter tuning is achieved using wavelength‐dependent time delay in a fiber medium by changing the Bragg wavelength of the fiber Bragg grating. The proposed microwave notch filter shows notch dips of more than 33 dB and has a tuning range from 828 to 905 MHz in a free spectral range with a wavelength change of 0.6 nm. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1328–1331, 2014

All optical SR and D flip-flop employing XGM effect in semiconductor optical amplifiers

This paper presents a simple and novel scheme for all-optical SR and D flip-flop employing cross gain modulation (XGM) effect in two wideband semiconductor optical amplifiers. The proposed flip-flop has a fast response, with less than 20ps transition times for both rising and falling edges. The FF speed-limit is mainly determined by the SOA recovery time and the intra-FF coupling length. The simulation results exhibit a contrast ratio of 13dB between two states with an AM of less than 2.5dB.The distinctive simplicity of the flip-flop implies reduced footprint and low power consumption which makes it ideal for photonic integration.

A Novel Method to Create a Wideband All-optical Wavelength Converter based on ASE of EDFA

We propose and demonstrate a newly wavelength converter based on EDFA. We use the intrinsic ASE and XGM effect which are produced by EDFA to convert the signal. This method doesn't need any SOA or probe light to generate a highly non-linear effect. The converted bandwidth includes the C- and L-band over optical communication systems. This novel converter also achieves the goal of an all-optical wavelength converter.

Investigation of optimum wavelength converter based on nonlinear polarisation rotation in a bulk SOA

This work is focused on understanding and optimising the physical mechanisms responsible for wavelength conversion based on cross-polarisation modulation (XPolM) in a bulk semiconductor optical amplifier. A comparison is made between the conversion performance that can be achieved with cross-gain modulation (XGM) and XPolM in co- and counter-propagation configurations. Wavelength independent conversion can be achieved when nonlinear polarisation rotation and XGM effects are balanced in the case of non-inverted wavelength conversion.

Comparison of Cross-Gain Modulation Effect of Manchester-Duobinary, RZ-DPSK, NRZ-DPSK, RZ, and NRZ Modulation Formats in SOAs

Conventional on-off keyed signals, such as return-to-zero (RZ) and nonreturn-to-zero (NRZ) signals are susceptible to cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) due to pattern effect. In this letter, XGM effect of Manchester-duobinary, RZ differential phase-shift keying (RZ-DPSK), NRZ-DPSK, RZ, and NRZ signals in SOAs were compared. The experimental results confirmed the reduction of crosstalk penalty in SOAs by using Manchester-duobinary signals

Comparison of conventional and gain-clamped semiconductor optical amplifiers for wavelength-division-multiplexed transmission systems

We compare the output spectra and data streams of a conventional 1550-nm semiconductor optical amplifier (SOA) with its gain-clamped (GCSOA) counterpart, in order to assess the impact of gain clamping on cross-gain modulation (XGM) and difference frequency generation (DFG). Whereas the conventional SOA exhibits a large amount of crosstalk due to XGM, there is virtually no XGM present in the GCSOA. However, the XGM effect in the SOA shows evidence of diminished efficiency at moderate input levels. We observe much higher DFG levels from the GCSOA (roughly 10 dB greater than the SOA). These DFG levels are such that cascaded wavelength cross-connect devices, in-line amplifiers, and even optical gates could experience inhibited performance.