An all-optical format conversion (AOFC) scheme for star-octal quadrature amplitude modulation (star-8QAM) signals is proposed and numerically simulated based on nonlinear effects in the high nonlinear fiber (HNLF). In the first stage AOFC processing, the input 30 Gbit/s star-8QAM signal is firstly de-aggregated into one 20 Gbit/s quadrature phase shift keying (QPSK) signal and one 10 Gbit/s typical on-off keying (OOK) signal by deploying the self-phase modulation (SPM), cross-phase modulation (XPM) and parametric amplification (PA) effects. In the second stage AOFC processing, the 20 Gbit/s QPSK signal and the 10 Gbit/s typical OOK signal are aggregated into one 30 Gbit/s star-8QAM signal again by utilizing the XPM and PA effects. Moreover, the amplitude ratio (AR) between the outer ring and inner rings of the aggregated star-8QAM signal can be adjusted flexibly by changing the QPSK and OOK signals power. Other octal modulation formats can also be generated through changing the QPSK and OOK signals power, including the rectangular 8QAM signals, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pi$</tex-math></inline-formula> /4-8QAM signals and 8-ary phase shift keying (8PSK) signals. Error vector magnitude (EVM) and bit error ratio (BER) for star-8QAM signals before and after AOFC are measured to analyse the scheme performance. The AOFC scheme provides the flexibility to adopt the appreciate modulation formats at the optical nodes to connect different optical networks. 

All-Optical Format Conversion for Star-8QAM Signals Based on Nonlinear Effects in Elastic Optical Networks

An all-optical format conversion scheme of 2-dimensional multiple-quadrature amplitude modulation (MQAM) to multiple-phase shift keying (MPSK) signals is proposed and numerically simulated by using the nonlinear Mach-Zehnder interferometer (MZI) configuration with wavelength preservation. The input octal-quadrature amplitude modulation (8QAM) signal is generated through the phase modulator (PM) and amplitude modulator (AM) and injected into the nonlinear MZI configuration. The designed nonlinear MZI configuration includes two 3 dB optical couplers (OCs), a piece of high nonlinear fiber (HNLF) and a variable optical attenuator (VOA) in the upper interfering arm and a piece of standard single mode fiber (SSMF) or tunable optical delay line (TODL) and a variable phase shifter (VPS) in the lower interfering arm. The converted octal-phase shift keying (8PSK) signal can be obtained from the nonlinear MZI configuration through vector superposition between the input optical signal and itself with some nonlinear phase shift. The needed asymmetric nonlinear phase shift is mainly induced by the big nonlinear index difference between HNLF and SSMF. The error vector magnitude (EVM) and bit error rate (BER) performance of the scheme are calculated before and after format conversion with the different input and receiver optical-signal-noise-ratios (OSNRs). The scheme can be used in the intermediate node to connect the different networks which adopt 8QAM and 8PSK signals, respectively. 

All-Optical Format Conversion of 2-Dimensional MQAM to MPSK Based on Nonlinear Mach-Zehnder Interferometer With Wavelength Preservation

An all-optical format conversion scheme of 2-dimensional multiple-quadrature amplitude modulation (MQAM) to multiple-phase shift keying (MPSK) signals is proposed and numerically simulated by using the nonlinear Mach-Zehnder interferometer (MZI) configuration with wavelength preservation. The input octal-quadrature amplitude modulation (8QAM) signal is generated through the phase modulator (PM) and amplitude modulator (AM) and injected into the nonlinear MZI configuration. The designed nonlinear MZI configuration includes two 3 dB optical couplers (OCs), a piece of high nonlinear fiber (HNLF) and a variable optical attenuator (VOA) in the upper interfering arm and a piece of standard single mode fiber (SSMF) or tunable optical delay line (TODL) and a variable phase shifter (VPS) in the lower interfering arm. The converted octal-phase shift keying (8PSK) signal can be obtained from the nonlinear MZI configuration through vector superposition between the input optical signal and itself with some nonlinear phase shift. The needed asymmetric nonlinear phase shift is mainly induced by the big nonlinear index difference between HNLF and SSMF. The error vector magnitude (EVM) and bit error rate (BER) performance of the scheme are calculated before and after format conversion with the different input and receiver optical-signal-noise-ratios (OSNRs). The scheme can be used in the intermediate node to connect the different networks which adopt 8QAM and 8PSK signals, respectively.

The cross-phase modulation (XPM) effect has been used to convert the amplitude-modulated signal to the phase-modulated signal in all-optical signal processing (AOSP). This paper mainly talks about the exact analytical solution of the converted phase-modulated signal by designing an all-optical format converter based on the XPM effect. In the designed simulation scheme, the input 8-ary quadrature amplitude modulation (8QAM) signal is converted into one binary phase shift keying (BPSK) signal due to the XPM effect. The power and phase transfer functions are described and plotted to prove the effectiveness of the simulation scheme. Error-vector-magnitude (EVM) and bit-error-rate (BER) of the optical signals before and after format conversion are measured to evaluate the scheme performance. Although the converted BPSK signal has worse EVM performance than the input 8QAM signal, it still can also obtain almost the same BER performance as the input 8QAM signal. The proposed scheme can be utilized at the intermediate network node (INN) connecting the different optical networks, which deploy to use the optical signals with different modulation formats.

Analytical Solution of All-Optical Format Conversion Based on the XPM Effect

An all-optical format conversion (AOFC) scheme for star-octal quadrature amplitude modulation (star-8QAM) signals is proposed and numerically simulated based on nonlinear effects in the high nonlinear fiber (HNLF). In the first stage AOFC processing, the input 30 Gbit/s star-8QAM signal is firstly de-aggregated into one 20 Gbit/s quadrature phase shift keying (QPSK) signal and one 10 Gbit/s typical on-off keying (OOK) signal by deploying the self-phase modulation (SPM), cross-phase modulation (XPM) and parametric amplification (PA) effects. In the second stage AOFC processing, the 20 Gbit/s QPSK signal and the 10 Gbit/s typical OOK signal are aggregated into one 30 Gbit/s star-8QAM signal again by utilizing the XPM and PA effects. Moreover, the amplitude ratio (AR) between the outer ring and inner rings of the aggregated star-8QAM signal can be adjusted flexibly by changing the QPSK and OOK signals power. Other octal modulation formats can also be generated through changing the QPSK and OOK signals power, including the rectangular 8QAM signals, $\pi$/4-8QAM signals and 8-ary phase shift keying (8PSK) signals. Error vector magnitude (EVM) and bit error ratio (BER) for star-8QAM signals before and after AOFC are measured to analyse the scheme performance. The AOFC scheme provides the flexibility to adopt the appreciate modulation formats at the optical nodes to connect different optical networks.

An all-optical aggregation and de-aggregation scheme between one 8-ary quadrature amplitude modulation (8QAM) signal and three binary phase shift keying (BPSK) signals is proposed and theory simulated based on nonlinear effects in high nonlinear fiber (HNLF). In this scheme, the input 8QAM signal is de-aggregated into three BPSK signals by deploying self-phase modulation (SPM), cross-phase modulation (XPM), four wave mixing (FWM) and parameter amplification (PA) effect. Firstly, an improved amplitude compression loop (ACL) is designed based on SPM effect to convert 8QAM signal into quadrature phase shift keying (QPSK) signal. A degenerate phase sensitive amplifier (PSA) based on FWM effect is used to decompose QPSK signal into the first two BPSK signals (BPSK-1 and BPSK-2). The third BPSK signal (BPSK-3) can be extracted from the probe light modulated in its phase by the input 8QAM signal thanks to XPM and PA effect. Secondly, BPSK-3 is converted into an atypical on-off keying (OOK) signal through a 1-bit delay interference (DI). BPSK-1 and BPSK-2 are recombined into one QPSK signal through a coupler. Finally, the recombined QPSK signal and the atypical OOK signal are aggregated into one 8QAM signal by using XPM and PA effect. The error vector magnitude (EVM) and bit error ratio (BER) of the 8QAM and BPSK signal before and after de-aggregation and aggregation are calculated to analyse the performance of the scheme. The scheme can be applied in the network node to connect different networks which explore to use 8QAM and BPSK signal respectively.

All-Optical Aggregation and De-Aggregation Between 8QAM and BPSK Signal Based on Nonlinear Effects in HNLF

An all-optical format conversion and regeneration scheme about 4-ary amplitude and phase shift keying (4APSK) signals is proposed and numerically simulated based on nonlinear effects in the high nonlinear fiber (HNLF). The input 4APSK signal is firstly converted into a regular quadrature phase shift keying (QPSK) signal by the nonlinear Mach-Zehnder interferometer (MZI) based on the self-phase modulation (SPM). Secondly, a degenerate phase-sensitive amplification (PSA) based on the four-wave mixing (FWM) is utilized to convert the regular-QPSK into two binary phase shift keying (BPSK) signals. The nonlinear MZI configuration is also used to compress the amplitude noise of BPSK. Thirdly, one phase shifter and one variable optical attenuator (VOA) are used to adjust the relative phase and power relationships of the two amplitude-regenerated BPSK signals. The regenerated 4APSK and converted QPSK signals can be generated in one 3-dB optical coupler through coherent addition of the two regenerated BPSK signals. The error-vector-magnitude (EVM) and the bit-error-rate (BER) are calculated and compared to evaluate the scheme performance. The proposed scheme can be applied as an optical regenerator or format convertor at the network gateway to increase the transmission distance or connect optical networks with different modulation formats.

https://ieeexplore.ieee.org/ielx7/4563994/4814557/10013684.pdf

Jiali Yang

Papers

All-Optical Aggregation and De-Aggregation Between 8QAM and BPSK Signal Based on Nonlinear Effects in HNLF

All-Optical Format Conversion of 2-Dimensional MQAM to MPSK Based on Nonlinear Mach-Zehnder Interferometer With Wavelength Preservation

All-Optical Format Conversion for Star-8QAM Signals Based on Nonlinear Effects in Elastic Optical Networks

All-Optical Regeneration and Format Conversion for 4APSK Signals Based on Nonlinear Effects in HNLF

All-optical aggregation and de-aggregation between OOK, QPSK and 8QAM signals based on nonlinear effects