Masanori Nakamura’s research while affiliated with Nippon Telegraph and Telephone and other places

... [25] presented analytical expressions for the two major methods of PPE, the correlation method (CM) and the minimum-mean-square-error (MMSE) method, and obtained a closed-form formula for the spatial resolution of CM. [25] also confirmed that MMSE approaches the true absolute power profile under a fine spatial step size but is more vulnerable to noise while CM only outputs the relative power profile but has a better noise robustness. Moreover, [26] quantitatively discussed the ill-posedness problem of MMSE-based PPE (MMSE-PPE) by evaluating the condition number of the nonlinear perturbation matrix, which more fully revealed the performance limitations of MMSE-PPE. Then, to balance the advantages of CM and MMSE, [27] proposed a generalized model of MMSE-PPE by introducing the Tikhonov regularization, which achieves a trade-off between noise robustness and power sensitivity. ...

Reference:

Derivation and analysis of power offset in fiber-longitudinal power profile estimation using pre-FEC hard-decision data

... and required for high data rate transmission for several applications such as video streaming and cloud computing [1][2][3]. To meet the demand of huge data transmission an L-band range of 1565-1625 nm and a U-band range of 1625-1675 nm [4] which have been suggested to use in [5]. However, this high band bandwidth, about 90 nm, has limited transmission distance due to the excessive noise and distortion [5]. ...

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Performance investigation of DP-EDFA amplifier for L + U-band optical communication systems

... Using a triple-band (SCL) WDM configuration, 115-Tb/s transmission over 100 km was reported with a 100-nm (12.5-GHz) continuous waveband using ultra-wideband semiconductor optical amplifiers (SOAs) [15]. Also using a triple band, greater than 150-Tb/s transmission [16] was first demonstrated with hybrid backward-pumped distributed Raman amplifier (DRA), Thulium-doped fiber amplifier (TDFA), and Erbium-doped fiber amplifier (EDFA) through G.652.D fiber standardized by The International Telecommunication Union -Telecommunication Standardization Sector (ITU-T), which has low-water peak characteristics around 1383 nm [35]. A DRA with a 1390-nm pump effectively compensated for the excess loss of S-band signals due to power transition from S to L bands caused by inter-band stimulated Raman scattering (SRS) [36]. ...

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Triple-Band WDM Transmission Beyond 100-Tb/s Capacity With 1-Tb/s/λ-Class Digital Coherent Channels

... Due to the huge demand of information bandwidth, optical communication systems are currently the default technology for long hall communication and rapidly penetrating the data centers as a unique solution that allows very high data rates with reasonable heat dissipation levels (Cheng et al., 2018;. The continuous increase in the data rate requires to multiplex different channels (Essiambre et al., 2010;Kobayashi et al., 2019). Different multiplexing techniques like: Wavelength Division Multiplexing WDM, Mode Division Multiplexing MDM and also Polarization Division Multiplexing PDM have been extensively studied in the literature Berdagué and Facq, 1982). ...

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Multilevel asymmetric coupler MAC polarization beam splitter for Si photonics technology

... Mixer-based electronic IFI-MUX (DBI) using three CMOS DACs in each signaling dimension has also been applied to coherent transmitters, achieving bit rates of up to 1.58 Tbps/λ [109], [110]. Another approach is based on RF-IQMs; it has been used in several high-symbol-rate transmission experiments with CMOS DACs [30], [111], [112], [113], [114], [115], [116], [117], [118]. Of course, CMOS DACs themselves have also been evolving; Up to 1.3 Tbps/λ has been reported with transmitters using one CMOS DAC for each dimension [119], [120], [121], [122], while the latest commercial DSPs seem to exhibit even higher capabilities. ...

Reference:

Analog Electronic and Optical Multiplexing Techniques for Transmitter Bandwidth Extension

... Ampli ers based on the DF or FWM effects are also generally called optical parametric ampli ers (OPAs). Periodically poled lithium niobate (PPLN) waveguide OPAs based on DF effect were widely investigated [56], leading to ultra-high-speed optical ber transmission beyond conventional telecommunication bands [57]. However, PPLN nonlinear waveguides are subject to signi cant challenges, such as di culties in fabrication (especially for low-loss arti cial periodic poling), dispersion engineering for ultra-wide band and high temperature sensitivity. ...

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Single-mode Dispersion-engineered Nonlinear Integrated Waveguides for Ultra-broadband Optical Amplification and Wavelength Conversion

... Unlike conventional OPM methods, which monitor only cumulative parameters [3][4][5][6][7][8] or require additional hardware such as optical time-domain reflectometry (OTDR), PPE reconstructs the signal's power evolution within the fiber link using solely communication data and receiver-side DSP, aided by a first-order nonlinear perturbation model [9]. This capability allows for the monitoring of span-wise power evolution [10,11], fiber loss and power anomalies [12,13], fiber type distinctions [14,15], optical amplifier gain spectra [16,17], passband narrowing [18], polarization dependent loss (PDL) [19,20], multi-path interference (MPI) [21], differential group delay (DGD) [22], interband stimulated Raman scattering-induced power transitions [23], and nonlinear signal-to-noise ratio (SNR) [24]. These diverse applications underscore PPE as a crucial technique in intelligent optical networks with integrated sensing and communication features. ...

Reference:

Derivation and analysis of power offset in fiber-longitudinal power profile estimation using pre-FEC hard-decision data

... Using one SiGe DAC at 1 sps in each signaling dimension, digital coherent transmissions at data rates of up to 1.96 Tbps/λ have been reported [123], [124], [125], [126], [127], [128]. BB-MUX systems with SiGe DACs have enhanced the bit rates up to 2.11 Tbps/λ [22], [23], [129], [130], [131], [132]. By combining a BB-MUX system with SiGe DACs and the mixerbased electronic IFI-MUX (DBI) systems, an even higher bit rate of 2.42 Tbps/λ has been reported [133]. ...

Reference:

Analog Electronic and Optical Multiplexing Techniques for Transmitter Bandwidth Extension

... Amplifiers based on the difference-frequency or FWM effects are also called optical parametric amplifiers (OPAs). Periodically poled lithium niobate waveguide OPAs based on the difference-frequency effect have been investigated 44 , leading to ultra-high-speed optical-fibre transmission beyond conventional telecommunication bands 45 . Based on the FWM process, OPAs using χ (3) -nonlinear nanophotonic waveguides are free of complicated periodic poling. ...

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Ultra-broadband optical amplification using nonlinear integrated waveguides

... This paper extends the work presented in [12], [22] with the following additional discussions: ...

Reference:

Linear Least Squares Estimation of Fiber-Longitudinal Optical Power Profile