Laser linewidths of the order 100 Hz are challenging to measure with existing technology. We propose a simple, efficient method ultra-narrow using dual-parameter acquisition based on partially coherent light interference. The linewidth is obtained two parameters that easily extracted from power spectrum. This reduces influence 1/f noise by utilizing kilometer-order-length delay fiber and independent fiber-length error for general situation. Simulation results show that, length less than 10%,...

We propose a simultaneous optical signal recognition (OSR) and signal-to-noise ratio (OSNR) monitoring method by using multi-task learning convolutional neural network (MTL-CNN) in conjunction with spectrums, which enables performance (OPM) the transmission network. In order to achieve trade-off between loss time consumption of MTL-CNN constructed for seven commonly used signals spectrum resolution 10 pm, number feature map channels four layers is delicately designed as 32, 64, 64 task...

The reference optical spectrum (ROS) based in-band signal-to-noise-ratio (OSNR) monitoring methods are accurate and inherently robust to fiber chromatic dispersion polarization mode dispersion. They also very simple suitable be deployed ubiquitously in the transmission system. In this paper, a ROS-based OSNR method is proposed for erbium doped amplifier (EDFA) amplified multispan dense wavelength division multiplexing systems with cascaded filtering effect (CFE) caused by add-drop filters or...

Digital coherent receivers adopting joint clock recovery and adaptive equalization (JCA) can avoid failures of the equalizer (AEQ) or algorithm (CRA) due to asynchrony chromatic dispersion (CD). But in previous JCA scheme, AEQ has a heavy computational load as it generate two samples per symbol (SPS) for subsequent timing phase error detector (TPED) which is core CRA. Furthermore, scheme cannot compensate receiver skew accommodate Nyquist signals with small roll-off factors (ROFs). These...

The free space optical communication (FSOC) signals often exhibit a much larger dynamic range and lower OSNR than fiber signals, due to the large-scale relative motion of terminals, change atmospheric channel conditions large transmission loss. For this reason flexible digital coherent receivers (DCR) capable adapting different have attracted attention in FSOC field. As timing recovery is indispensable for DCRs, development algorithm (TRA) processing such particular interest In paper we...

A clock recovery algorithm (CRA) suitable for non-integer oversampled Nyquist signals with a small roll-off factor (ROF) is appealing to short-reach high-speed inter-datacenter transmission systems which need cut down the transceiver power consumption and cost by reducing oversampling (OSF) using cheap low-bandwidth components. However, due lack of timing phase error detector (TPED), CRAs proposed now fail OSFs below two ROFs close zero are not hardware-efficient. To solve these problems, we...

Digital coherent combining (DCC) technique can increase the free space optical signal collection area by signals received an array of small apertures in a manner. To realize DCC different versions must be aligned phase digital alignment algorithm (PAA). Low computation complexity is imperative for PAA because main obstacle to implement and real-time manner availability processing (DSP) circuits offering very high gate density speed. In this paper we investigate relationship between...

Optical spectrum (OS) is a vital characteristic of optical signals. Ultra-high resolution (UHR) OS can provide more detailed and accurate information for performance monitoring link quality diagnosis. By comparing actual signal UHR-OS observed at in-line points with the theoretical ideal ones, various distortions be readily identified accurately estimated. But in future flexible heterogeneous networks signals different symbol rates, modulation formats pulse shaping schemes may coexist same...

In free space optical communication systems, multi-aperture coherent receivers based on digital beam combining (D-CBC) technique can provide exceptionally high sensitivity and are more robust to the atmosphere turbulence compared with single aperture same collection area. D-CBC relies phase alignment algorithm (PAA) align different versions of signals in phase. However, due limited working frequency signal processing (DSP) circuits, main obstacle realizing real-time multiple high-speed is...

A versatile digital coherent receiver capable of handling optical signals with different kinds pulse shaping schemes (PSSs) is indispensable for future flexible and heterogeneous communication networks. Therefore, a low-complexity timing phase error detector (TPED) all PSSs particular interest. In this paper, we propose TPED suitable both Nyquist roll-off factors non-Nyquist signals. It requires two samples per symbol involves no multiplications. As far as know, it has the lowest computation...

In this paper a method is proposed to maximize the bandwidth of WDM router based on one-pump fiber parametric wavelength converters. It proved that for such converters there exists an optimum signal (idler) frequency at which output (input) tuning range can be maximized. Analytical expressions and maximal are deduced. Then two-stage bidirectional conversion proposed. With converter significantly improved compared one-stage ones by 252% if ordinary highly nonlinear fibers used or 390% with...

Brillouin optical spectrum analyzer (BOSA) based on stimulated scattering (SBS) can provide ultra-high resolution, which in theory greatly improve the signal-to-noise ratio (OSNR) measurement accuracy, especially for systems with close channel spacing and cascaded filtering effect (CFE). BOSA utilizes narrow bandwidth SBS as an active band-pass filter (A-OBPF); thus, unwanted out-of-band spectral components are actually not completely suppressed may account unneglectable proportion of power...

This letter represents a highly sensitive all-optical chromatic dispersion (CD) monitoring method utilizing phase-matched four-wave mixing (FWM) in nonlinear optical fibers (HNLFs). The ability arises from the exponential FWM gain which provides an power transfer function (PTF) mapping CD experienced by signals onto average of output idler wave. Our is simple and much more compared to other PTF-based methods proposed before. sensitivity enhancement important for accurate compensation makes...

The in-band OSNR monitoring methods based on the noise-free reference optical spectrum (ROS) have attracted much attention in field of performance because they are cost-effective and insensitive to chromatic dispersion polarization mode dispersion. In this paper, we propose a new ROS method that is robust distortions due non-ideal modulation, variations in-line EDFA gain number filtering elements traversed by signal. Moreover, supports using standard retrieved existing machine-learning...

We present a new approach to the design of holey fibers that have ultra-high nonlinearity and dispersion properties optimized for tunable fiber parametric wavelength converters based on degenerated four wave mixing. This hybrid combines downhill simplex algorithms with mixing modeling. Exploiting relations between converter's characteristics, this method is not only much faster than other methods proposed before but also enables an inverse according pre-set device like conversion gain,...

Single-photodiode-per-polarization coherent receivers (SCRs) can preserve all of the merits conventional digital (DCRs) such as supporting chromatic dispersion (CD) compensation and polarization multiplexing, whilst have much lower optical complexity. But overall algorithm complexity SCRs is relatively higher because an extra dedicated field reconstruction (FRA) required in addition to standard algorithms used DCRs. The heavy computation burden introduced by FRA poses a major obstacle reduce...

A symbol rate identification method is proposed for optical signals with commonly used modulation formats. Numerical simulation and experimental results show it accurate robust to different link impairments.