Optical Signal-to-noise Ratio Research Articles

Estimation of spectral spacing and linear ICI effects using IQ constellation images and CNN in gridless WDM systems

The estimation of spectral spacing (guard band) among optical channels in gridless WDM systems would be decisive for making swift decisions in reconfigurable optical add-drop multiplexers (ROADMs) to avoid linear interchannel interference (ICI) effects during the channel aggregation process in transit nodes. In this work, we propose a method based on the construction of heat scatter images from constellation diagrams along with convolutional neuronal networks (CNN) to identify when optical channels are spectrally overlapped as well as the value in GHz of the channel separation in a specific optical channel without adjacent channels information. We validate our method in a gridless 16-QAM Nyquist-WDM system with different channel spacing and optical signal-to-noise ratio (OSNR). Experimental results demonstrated that overlap detection can be achieved with 3×16GBd accuracy. Additionally, the estimation of spectral spacing achieved an error (RMSE) of less than 0.6 GHz. The penalty in accuracy and RMSE is only ∼98% and , respectively, when there is no knowledge of the OSNR value. Thus, this method has the potential to be integrated into monitoring tools designed for future dynamic gridless optical transmission systems.

Design of a Novel 31.5 THz Bandwidth Hybrid TDFA-HDFA at 2000 nm and Its Applications in Unregenerated DWDM Lightwave Transmission Systems

We report design and applications of a novel multi-Watt (> 1 Watt output power) 2000 nm band hybrid Thulium- and Holmium-doped fiber amplifier with record wideband 380 nm (31.5 THz) continuously operating bandwidth from 1720-2100 nm. We outline the theory, physics, and simulations behind this design, and show by comparison with previously published experimental results that the design presented is accurate to within ± 0.5 dB in saturated output power and ± 1.0 dB in small signal gain. Applications in future ~300-400 nm bandwidth wideband 2000 nm Pb/s DWDM lightwave fiber optical transmission systems spanning 10,000 km using new hollow core fiber designs are discussed. In particular, we demonstrate robust beginning-of-life optical signal to noise ratio (OSNR) and Q-factor margins for designs of 0.161 Pb/s DWDM unregenerated (without optical-to-electrical-to-optical or O-E-O electronic functions) all-optical transmission in the 2000 nm band over 10,000 km for representative terrestrial and submarine lightwave applications. We achieve a total capacity × distance product of 1608 Pb/s. km (1.61 Exabits/s. km) over a single one-core optical fiber for the 10,000 km system designs. Applications to designs of 40,000 km deployable unregenerated all-optical DWDM 0.124 Pb/s subsea lightwave transmission systems with 5.21 Exabit/s. km capacity × distance product are outlined. Received: 9 September 2024 | Revised: 10 December 2024 | Accepted: 26 December 2024 Conflicts of Interest The author declares that he has no conflicts of interest to this work. Data Availability Statement Exail Tm- and Ho-doped gain fiber specifications are openly available at https://cybel-llc.com/wp-content/uploads/2021/06/IXF-HDF-PM-8-125_edA-Ho-SC-doped-PM-fiber.pdf and https://cybel-llc.com/wp-content/uploads/2021/06/IXF-TDF-PM-5-125_edA-Tm-SC-doped-PM-fiber.pdf. Data of the component devices in Table 1 are openly available at https://retandassociatesllc.com/wp-content/uploads/2024/04/GSLEOP2022-Presentation-RET-v.11-08222022.pdf. Other data are available from the corresponding author upon reasonable request. Author Contribution Statement Robert E. Tench: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition.

All-fiber E + S band continuously tunable bismuth-doped germanosilicate fiber laser

In this Letter, we present an all-fiber bismuth (Bi)-doped germanosilicate fiber laser that is continuously tunable within the range of 1425–1475 nm, enabled by a tunable optical filter. A maximum output power of 86.4 mW was achieved at 1450 nm with a slope efficiency of 13.7%. It is, to the best of our knowledge, the first demonstration of an all-fiber tunable continuous-wave (CW) bismuth-doped fiber laser (BDFL) operating in the E + S band. Moreover, a bismuth-doped fiber amplifier (BDFA) was constructed to further scale the laser output power to 159.2 mW with a 21% slope efficiency. Across the 1425–1475 nm range, we achieved >117 mW output power with >50 dB in-band optical signal-to-noise ratio (OSNR).

Analysis of bit error rate and receiver sensitivity of a DC biased optical OFDM transmission link using single mode fiber with distributed Raman amplifier

Abstract In this paper, an analytical method is presented to assess the performance of bit error rate (BER) of a DC biased optical orthogonal frequency division multiplexing (DCO-OFDM) SMF transmission with distributed Raman amplifier (DRA). Formulas are developed to determine the signal-to-noise ratio (SNR) at the output of a DCO-OFDM receiver and the bit error rate (BER) for an OFDM demodulator’s output. By considering the Gaussian probability density function (pdf) for the OFDM demodulator output, the average BER is calculated numerically. The results are presented based on receiver sensitivity, bit error rate and optical SNR at a given BER of 10−9, with variations in system parameters such as input signal power, data rate, fiber distance, modulation index and OFDM sub-channel number. A comparison of BER performance indicates that DC biased optical OFDM with intensity modulation direct detection (DCO-DD-OFDM) offers better receiver sensitivity compared to optical OFDM without DC bias at a BER of 10−9. Our analytical results align with the published findings on optical OFDM.

Single-longitudinal mode quadruple wavelength C+L-band erbium-doped fiber laser based on the pairs of reflective fiber bragg gratings

Abstract Flatness of lasing wavelengths of a multi-wavelength fiber laser (MWFL) is an important design constraint that is considered attractive in various applications of photonics and optical communication systems. In this work, we propose a single-longitudinal mode (SLM) quadruple wavelength C+L-band Erbium-doped fiber laser (EDFL) with high output power flatness. It is implemented with a short piece of Erbium-doped fiber (EDF) pumped by conventional 980 nm laser diode and four pairs of reflective fiber Bragg gratings (FBGs) through numerical simulations. The reflectivities of FBGs are adjusted such that SLM quadruple wavelengths are obtained at the output of EDFL with flatness of 0.9 dB, optical signal-to-noise ratio (OSNR) in the range of 44.5–53.2 dB, and linewidths (LWs) in the range of 5.4–7.3 MHz. Slope efficiency (SE) of around 24% is achieved considering the total power of all lasing wavelengths generated. Moreover, the power variation around 0.1 dB for lasing wavelengths of 1540.2 nm and 1605.7 nm is noticed for twelve iterations each repeating after five-minute interval. The proposed SLM quadruple wavelength EDFL has promising application prospects for distributed sensing and optical communication systems due to excellent performance metrics.

Design and performance evaluation of a hybrid FSO-FTTx communication link utilizing UD-WDMA 1.28 Tbps data rates transmission under various weather conditions

Abstract The rapid growth of high-data-rate applications necessitates the development of new communication frameworks since bandwidth constraints for data-intensive applications hinder traditional networks and conventional microwave/radio frequency (RF) communications. This study explores a hybrid communication link that combines fiber-to-the-x (FTTx) and free-space optical (FSO) technologies, utilizing ultra-dense wavelength-division multiple access (UD-WDMA) with a channel spacing of 0.2 nm/25 GHz, under various weather conditions. Based on bit error rate (BER), optical signal-to-noise ratio (OSNR), and quality factor (QF), the performance of the suggested FSO-FTTx system was examined. The system performed well in diverse weather conditions, achieving a minimum BER of ≤10−5, QF values of 4 or higher, and OSNR levels between 10 and 20 dB. The proposed system successfully transmitted a data rate of 1.28 Tbps over 35 km in single-mode fiber (SMF), accommodating different FSO link ranges despite varying weather conditions. However, performance fluctuations were observed under adverse conditions, with attenuation ranging from 0.91 dB/km in extremely light mist to 273.39 dB/km in dense fog, impacting the FSO link range. The findings underscore the proposed hybrid system’s potential to enhance optical wireless communication for high data rates, making it promising for beyond 5G and early 6G applications.

Single-longitudinal-mode self-seeded Brillouin fiber laser with an ultra-narrow linewidth achieved utilizing a triple-ring resonator

What we believe to be a novel single longitudinal mode (SLM) triple-ring (T-R) self-seeded Brillouin fiber laser (BFL) featuring outstanding stability, an ultra-narrow linewidth, and a high optical signal-to-noise ratio (OSNR) is proposed and experimentally investigated in this study. The key innovation in this design is eliminating the need for an additional costly ultra-narrow linewidth pump source typically required in conventional BFL. Instead, the laser preferentially excites stimulated Brillouin scattering (SBS) in the fiber through the self-seeded cavity mode dominant in the cavity. This approach generates Brillouin stokes and leverages the Vernier effect of the T-R resonator structure to suppress multimode oscillations, ensuring the generation of a Brillouin laser with an ultra-narrow linewidth and enabling SLM operation. The experimental results show that with the output power of 980-nm LD fixed at 400 mw, the OSNR of the self-seeded BFL spectrum reaches 54 dB, and the side mode suppression ratio (SMSR) is 22 dB. The -3 dB linewidth of the self-seeded BFL can be measured by the heterodyne beat frequency method at 30 Hz, and the output power and wavelength fluctuations are lower than 1.318 dB and ±0.007 nm, respectively, during the sixty minutes observation period. Additionally, the wavelength of the self-seeded BFL can be flexibly tuned within the range of 1560 – 1575 nm. This innovative approach demonstrates significant theoretical and practical implications for the development of low-cost, high-performance BFL systems compared to traditional BFL methods.

Wavelength-Switchable 2 μm Single-Longitudinal-Mode Thulium-Doped Fiber Laser Based on Dual-Active Cavity and DLTCTR

A thulium-doped fiber laser (TDFL) with a dual-active cavity and a directly linked three-coupler triple-ring filter is designed and demonstrated. Its operational principle is analyzed, and a corresponding experimental setup is built. Eleven single-wavelength laser outputs with a single-longitudinal-mode (SLM) output near 2 μm are obtained. The laser output covers a wavelength range from 1933.95 nm to 1971.76 nm, with a continuous switchable output range of 37.81 nm and a minimum center wavelength interval of 0.22 nm. The optical signal-to-noise ratio (OSNR) of the output laser within the tuning range is >48.53 dB, and its maximum OSNR is 70.24 dB. The minimum wavelength fluctuation is 0.03 nm, and the power fluctuation is between 0.15 and 2.61 dB. A single wavelength with a center wavelength of 1933.95 nm is monitored for 75 min, and the radio-frequency spectrum is scanned 27 times within the frequency range of 0 to 400 MHz. The results demonstrate that the TDFL can operate continuously and stably in an SLM state. The linewidth and linewidth fluctuation of the TDFL are measured, and the minimum linewidth, corresponding to a measurement time of 0.001 s, is 65.14 kHz. The experimental results show that the proposed TDFL has a high OSNR and excellent wavelength-switching ability, and its SLM operation is very stable.

Scalable SOA-based Banyan optical space switch on InP membrane on silicon (IMOS).

Optical switches (OS) are vital for meeting modern data centers' capacity and latency needs, overcoming the bandwidth and speed limitations that electronic switches encounter. To this end, this work proposes a semiconductor optical amplifier (SOA)-based OS on the IMOS, a unique platform with a combination of high refractive index contrast for compactness and monolithic active-passive integration for active functionalities, thereby enabling the creation of compact SOA-based OSes. An 8 × 8 Banyan SOA-based OS is integrated on a 4 × 4 mm2 area on the standard 4 × 6 mm2 IMOS cell. This marks the first application of the IMOS technology platform for SOA-based OSes and sets the stage for compact and large-scale monolithic photonic integrated OS circuits. The basic 2 × 2 switch module delivers a high optical signal-to-noise ratio (OSNR) and an extinction ratio (ER) above 45 dB. Employing NRZ-OOK routing on the 2 × 2 basic OS module, a 15 dB input power dynamic range (IPDR) is achieved within a 1 dB power penalty at 12.5 Gb/s. Data routing at higher data rates of 25 Gb/s and 40 Gb/s incurs power penalties of 0.8 and 1.4 dB, respectively. Furthermore, data routing for a 3-stage 8 × 8 switch operating at 25 Gb/s results in a power penalty of 1.2 dB. Compared to the 1-stage 2 × 2 switch, only a 0.4 dB additional penalty is observed despite incorporating 2 additional SOAs in the cascade. This indicates that the switch can scale to higher radix to accommodate multi-stage switches with numerous ports, large bandwidth, and fast speed, which is essential in modern large-scale data centers.

Maximizing transmission capacity in optical communication systems utilizing a microresonator comb laser source with adaptive modulation and bandwidth allocation strategies

Traditional optical communication systems employ bulky laser arrays that lack coherence and are prone to severe frequency drift. Dissipative Kerr soliton microcombs offer numerous evenly spaced optical carriers with a high optical signal-to-noise ratio (OSNR) and coherence in chip-scale packages, potentially addressing the limitations of traditional wavelength division multiplexing (WDM) sources. However, soliton microcombs exhibit inhomogeneous OSNR and linewidth distributions across the spectra, leading to variable communication performance under uniform modulation schemes. Here, we demonstrate, for the first time, to our knowledge, the application of adaptive modulation and bandwidth allocation strategies in optical frequency comb (OFC) communication systems to optimize modulation schemes based on OSNR, linewidth, and channel bandwidth, thereby maximizing capacity. Experimental verification demonstrates that the method enhances spectral efficiency from 1.6 to 2.31 bit ⋅ s−1 ⋅ Hz−1, signifying a 44.58% augmentation. Using a single-soliton microcomb as the light source, we achieve a maximum communication capacity of 10.68 Tbps after 40 km of transmission in the C-band, with the maximum single-channel capacity reaching 432 Gbps. The projected combined transmission capacity for the C- and L-bands could surpass 20 Tbps. The proposed strategies demonstrate promising potential of utilizing soliton microcombs as future light sources in next-generation optical communication.

Fiber-optic radio frequency transfer with enhanced frequency stability using fiber Brillouin amplifiers.

The frequency stability of long-distance two-way fiber-optic radio frequency (RF) transfer is directly affected by the optical signal-to-noise ratio (OSNR) of optical amplifiers. In this paper, we have proposed a stimulated Brillouin scattering (SBS)-based optical amplification scheme with high OSNR for two-way fiber-optic RF frequency transfer over single mode fibers (SMF). At the remote and local site, the modulated carrier transferred from the opposite was amplified and then frequency upshifted by Brillouin frequency shift (BFS) for pump generation. This approach can avoid the use of additional pump lasers and phase-locked loops for wavelength stabilization of the pump. The pump was injected into the fiber link and counter-propagated with the signal to amplify the modulated carrier. A 2.2 GHz RF signal transfer with the proposed SBS-based optical amplification schemes was demonstrated over a 100 km fiber link. The experimental results illustrated that the OSNR was increased by 35 dB and 32 dB at the local site and the remote site, respectively, compared to the results obtained with erbium-doped fiber amplifiers (EDFA)-based optical amplification. Benefiting from improved OSNR, the frequency stability was increased by more than one order of magnitude below 1000 s averaging time, and the phase noise was reduced to the noise floor below 0.1 Hz offset frequency. The proposed optical signal amplification approach has a potential application for transferring atomic clocks over long-haul fiber links.

A Tunable and Switchable Multi-Wavelength Erbium-Doped Fiber Ring Laser Enabled by Adjusting the Spectral Fringe Visibility of a Mach-Zehnder Fiber Interferometer

This paper presents a tunable, switchable multi-wavelength emission from an erbium-doped fiber ring laser, enabled by adjusting the spectral fringe visibility of a fiber interferometer filter. The filter is formed with specially designed concatenated tapered fibers to configure a Mach-Zehnder fiber interferometer (MZFI). The laser emission is highly flexible and reconfigurable, allowing for tuning between single- and dual-wavelength operation. The laser can switch sequentially from one up to six wavelengths by fixing the curvature and adjusting the polarization state. The lasing emission is generated over a stable wavelength range between 1559.59 nm and 1563.54 nm, exhibiting an optical signal-to-noise ratio (OSNR) exceeding ~35 dB. The performance of amplitude and wavelength fluctuations were evaluated, indicating an appropriate stability of ~3 dB and a shift less than 0.1 nm within a 45 min period at room temperature. A detailed comparison with the literature is given.

Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser. The slope efficiency reached 25.30% for the absorbed pump power. The optical signal-to-noise ratio (OSNR) of the laser was ∼69.78 dB, and the laser linewidth was ∼84.5 kHz. Additionally, the measured relative intensity noise (RIN) remained at -130 dB/Hz at frequencies above 9 MHz. The experimental results indicate that the TCDSF is a promising gain medium for single-frequency lasers at 1.7 µm.

Transfer learning-assisted modulation classification and OSNR estimation using constellation diagrams

Abstract A cost-effective deep transfer learning (TL) learned with characteristics derived from the constellation diagram is proposed for executing modulation classification and optical signal-to-noise ratio (OSNR) estimation for the future generation of elastic optical networks. The information acquired with the ImageNet dataset is transferred using pre-trained TL versions including VGG19, ResNet152V2, InceptionV3, and ResNet50 to identify various modulation formats and their corresponding OSNR. Adam optimizer is employed to ascertain the appropriate settings for the hyperparameters. Numerical results demonstrate that the proposed VGG19 method achieves the highest level of accuracy (100%) in the recognition of various modulation forms. To fulfil the requirements of actual use, OSNR monitoring is also explored, with a total precision equal to 95.2%. Furthermore, a thorough investigation of the impact of training data dimensions, on TL performance is conducted. The outcomes of the proposed method demonstrate that the suggested TL-based algorithms are more accurate and need much less training and testing time than non-TL approaches.

Performance Comparison of Seed Generation Techniques of Stimulated Brillouin Scattering-Based Microwave Photonics Amplifier and Filter

This work presents a Brillouin amplification performance comparison of seed generation techniques using double-sideband suppressed carrier (DSB-SC) and single-sideband suppressed carrier (SSB-SC) modulations. The SSB-SC is obtained using an optical bandpass filter (OBPF) and in-phase and quadrature Mach-Zehnder modulator (IQ-MZM). All three techniques provide high amplification performance with optical signal-to-noise ratio (OSNR) enhancement of 37.47 dB, 33.14 dB, and 32.67 dB using DSB-SC, SSB-SC/OBPF, and SSB-SC/IQ-MZM, respectively. The best seed generation technique is using the DSB with a signal amplification of 62.47 dB. The technique presents ~4 dB higher OSNR enhancement due to the dual-energy transfer obtained from the beating process of the DSB than SSB. A ~3 dB OSNR reduction is found when pump linewidth (LW) was changed from 1kHz to 50 MHz, which suggests using a low-cost pump source whenever the OSNR reduction is not critical. The work also shows that the three techniques required 10 dBm stimulated Brillouin scattering threshold (SBST) to stimulate the process. An additional analysis of DSB-SC shows that a high-carrier suppression during the seed generation technique using MZMs is insignificant to the amplification performance. The high-carrier suppression produces a high seed signal power that distorts the Brillouin gain spectrum (BGS) and the pump depletion region, hence reducing the Brillouin gain (BG). Since carrier suppression is not a primary consideration, a cost-effective MZM with a modest extinction ratio requirement is allowed. The relaxed requirement of the pump’s linewidth and MZM’s extinction ratio suggest a cost-effective development of the SBS-based optical amplifier with narrow filter bandwidth.

C + L-band tunable sub-kHz linewidth single frequency fiber laser by combining a fiber sub-ring with a saturable absorber

A sub-kHz linewidth single-frequency fiber laser that can be tuned in the full range of C + L band is proposed and experimentally demonstrated. A broad band gain fiber by bidirectional pumping combining with a wide tunable filter is used to realize 75.87 nm tuning range from 1529.98 to 1605.85 nm, which can be further improved if a wider tunable filter is available. To achieve single-frequency ultra-narrow linewidth laser operation, a ring-cavity laser configuration with a fiber sub-ring and a saturable absorber is utilized. The measured optical signal-to-noise ratio (OSNR) of the fiber laser is over 80 dB, the side mode suppression ratio (SMSR) can be improved to ∼60 dB, and the linewidth can be narrowed to ∼453 Hz. The output power of the laser exceeds 28 mW, and the slope efficiency is 2.05 %. This proposed fiber laser has the advantages of narrow linewidth, excellent wavelength tunability, and high output power, which is promising for the applications in optical sensing and optical communication systems.

Multicore fiber design housing a fluorine-doped low-latency core and cutoff shifted cores

Design of heterogeneous 4-core fiber housing a low-latency core and conventional cutoff shifted cores in a standard 125-μm cladding diameter is investigated to enable signal processing delay reduction using common mode impairment. For the low-latency core, 1-μs propagation delay reduction and an optical signal-to-noise ratio (OSNR) comparable to or greater than that of cutoff shifted cores are required. In this paper, we consider an F-doped core and depressed cladding structure with a large effective area as the low-latency core. It can be expected to achieve sufficient group delay reduction of the low-latency core, the OSNR unification among heterogeneous cores, and low inter-core crosstalk in a standard 125-μm cladding diameter. Consequently, we revealed the optimized low-latency core achieving the group delay reduction of 1 μs and the OSNR as same level as the cutoff shifted cores as we expected. The designed heterogeneous 4-core fiber with the standard 125-μm cladding diameter suppressed the inter-core crosstalk to be low enough to support a 1,000-km long transmission. We expect the figure-of-merit (FoM) of the 4-core fiber to be as high as previously reported 4-core fibers, and the FoM improvement are found when the low latency core and cutoff shifted core are placed alternately thanks to the core heterogeneity.

Stable and Tunable Erbium Ring Laser by Rayleigh Backscattering Feedback and Saturable Absorber for Single-Mode Operation

This work demonstrates a high-quality erbium-doped fiber (EDF) ring laser in the L-band gain range by combining the Rayleigh backscattering (RB) feedback signal and unpumped EDF induced saturable absorber (SA) filter. The optical filter effect induced by the RB feedback injection and EDF SA could generate single-longitudinal-mode (SLM) behavior and shrink the linewidth to sub-kHz. The output linewidth, power, and optical-signal-to-noise ratio (OSNR) of the fiber ring laser were also shown within the 42 nm wavelength bandwidth of 1565.0 to 1607.0 nm. Also, the instabilities of output power and central wavelength of each lasing lightwave were analyzed with a measurement time of 45 min.

Enhancing C+L-band transmission performance through OSNR flatting and link damage recovery algorithms.

The rapid growth of data-intensive services has driven the need for high-capacity optical networks. C+L band optical communication systems have emerged as a potential solution by extending the operational bandwidth. However, the wider spectrum introduces significant stimulated Raman scattering (SRS) effects that impact signal power profile, Kerr nonlinearity, and amplified spontaneous emission (ASE) noise. To address these challenges, this paper proposes an optical power control strategy designed to achieve a flat optical signal-to-noise ratio (OSNR) across all transmitted channels, which is particularly effective in mitigating SRS effects in C+L band systems. Furthermore, a link damage recovery algorithm is developed to ensure system robustness against localized fiber degradations. Extensive simulations are conducted to compare the performance of the proposed strategy with the conventional flat launch power approach under single-span and multi-span transmission scenarios. The results demonstrate that the proposed strategy achieves a higher minimum generalized signal-to-noise ratio (GSNR), exhibits stronger resilience to link damage across a wide range of transmission conditions.

Using ADTS and CNN methods to effectively monitor CD, crosstalk, and OSNR in an optical network

The article presents the results of a method based on asynchronous delay-tap sampling (ADTS) and convolutional neural network (CNN) for determining simultaneously occurring disturbances described using the chromatic dispersion (CD), crosstalk and optical signal-to-noise ratio (OSNR) parameters. The ADTS method was used to generate training and test data for the convolutional network, which in turn was used to learn to recognize interference from said data. The tests were carried out for a transmission speed of 10 Gbit/s and for on-off keying (OOK) and differential phase shift keying (DPSK) modulation. Very good results were obtained in recognizing simultaneously occurring phenomena. Accuracy of over 99% was achieved for CD and crosstalk for DPSK modulation and over 98% for OOK modulation. In the case of amplified spontaneous emission (ASE) noise, slightly weaker results were obtained, above 95–96% for both modulations. Based on the conducted research, it was determined that the use of ADTS and CNN methods enables monitoring of simultaneously occurring CD, crosstalk, and ASE noise in the physical layer of the optical network, while maintaining the requirements for modern monitoring systems.