Linearisation Method of DML-Based Transmitters for Optical Communications Part I: Theory and Simulation Studies

Bamiedakis, N.; Cunningham, David; Penty, R.V.

doi:10.1109/jlt.2021.3093517

Cited by 4 publications

(28 citation statements)

References 35 publications

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“…The constant terms of the expression are grouped in the sub-current. The exact expressions that define each sub-current were presented in Part I [19].…”

Section: A Basic Theorymentioning

confidence: 99%

“…Using these simplifications, and can be readily derived from the linear sub-current via simple operations: differentiation, gain and time shift. The method was described in detail in Part I [19] and possible hardware implementations were discussed in Part II [20].…”

Section: A Basic Theorymentioning

confidence: 99%

“…The parameters and are constants that depend only on the laser parameters, while the parameter is a scaling factor that depends on both the laser parameters and the operating point. These can be found analytically using the equations provided in Part I [19]. It is assumed that the laser parameters are either known by design or can be estimated through measurements.…”

Section: A Basic Theorymentioning

confidence: 99%

“…We have developed a new linearization method of optical transmitters based on DMLs, named the "Stretched A" (StrA) method, which can be easily implemented in practice [19,20]. The method generates a modulating current waveform that approximates the ideal modulating current that produces a linear optical output waveform [14].…”

mentioning

confidence: 99%

“…The method efficiently corrects most of the laser non-linearity while featuring large tolerances. In Parts I [19] and II [20] of this work, we presented its theoretical background. We reported detailed simulation and experimental studies on its use in an optical link using a vertical-cavity surface-emitting laser (VCSEL) and non-return-to-zero (NRZ) modulation.…”

mentioning

confidence: 99%

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Linearisation Method of DML-Based Transmitters for Optical Communications Part III: Pulse Amplitude Modulation

Bamiedakis

Cunningham

Penty

2021

J. Lightwave Technol.

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A new linearization method for optical transmitters based on directly modulated lasers (DMLs), named the Stretched A method, was proposed in Parts I and II of this work. Parts I and II presented the theoretical framework of the method for non-return-to-zero (NRZ) modulation and related detailed simulation and experimental results. Here, we extend the method to pulse amplitude modulation schemes (PAM). Focussing on 4level PAM (PAM-4), we present the theoretical background and discuss implementations options. A simplified variation of the method for the generation of PAM signals with a significantly lower number of sub-currents is proposed. Simulation studies for PAM-4 transmission at 50 GBaud (100 Gb/s) and an experimental proof-of-principle demonstration at 16 GBaud (32 Gb/s) are reported based on 850 nm vertical-cavity surfaceemitting lasers (VCSELs). For PAM-4, products of effective eye diagram areas ( ) of 0.6×10 -5 and 43×10 -5 before and after applying the Stretched A method were measured, demonstrating an improvement ratio of ~72. The sensitivity and tolerances of the method are analyzed using simulation and experiment.

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“…The constant terms of the expression are grouped in the sub-current. The exact expressions that define each sub-current were presented in Part I [19].…”

Section: A Basic Theorymentioning

confidence: 99%

Section: A Basic Theorymentioning

confidence: 99%

Section: A Basic Theorymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Linearisation Method of DML-Based Transmitters for Optical Communications Part III: Pulse Amplitude Modulation

Bamiedakis

Cunningham

Penty

2021

J. Lightwave Technol.

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Linearisation Method of DML-based Transmitters for Optical Communications Part II: Experimental Demonstration and Implementation Methods

Bamiedakis

Cunningham

Penty

2021

J. Lightwave Technol.

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In this paper, we report the first experimental demonstration of the Stretched A linearisation method. The theoretical framework of the method and related simulation studies have been presented in Part I of this work. Here, we apply the method on an 850 nm multimode vertical-cavity surfaceemitting laser (VCSEL) specified for operation at 10 Gb/s and demonstrate good quality optical output waveforms with little non-linear distortion at 16 Gb/s using non-return-to-zero (NRZ) modulation. An experimental sensitivity analysis on the generation of the required modulating current components demonstrates large tolerance to parameter mismatch. In addition, it is shown that an adaptive gain scheme can improve the tolerance to the timing offset between the current components. Potential hardware implementations using either analog or digital electronics are also discussed.

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End-to-end optimization of optical communication systems based on directly modulated lasers

Hernandez,

Peucheret,

Da Ros

et al. 2024

J. Opt. Commun. Netw.

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The use of directly modulated lasers (DMLs) is attractive in low-power, cost-constrained short-reach optical links. However, their limited modulation bandwidth can induce waveform distortion, undermining their data throughput. Traditional distortion mitigation techniques have relied mainly on the separate training of transmitter-side pre-distortion and receiver-side equalization. This approach overlooks the potential gains obtained by simultaneous optimization of the transmitter (constellation and pulse shaping) and receiver (equalization and symbol demapping). Moreover, in the context of DML operation, the choice of laser-driving configuration parameters such as the bias current and peak-to-peak modulation current has a significant impact on system performance. We propose, to our knowledge, a novel end-to-end optimization approach for DML systems, incorporating the learning of bias and peak-to-peak modulation current to the optimization of constellation points, pulse shaping, and equalization. The simulation of the DML dynamics is based on the use of the laser rate equations at symbol rates between 15 and 25 Gbaud. The resulting output sequences from the rate equations are used to build a differentiable data-driven model, simplifying the calculation of gradients needed for end-to-end optimization. The proposed end-to-end approach is compared to three additional benchmark approaches: the uncompensated system without equalization, a receiver-side finite impulse response equalization approach, and an end-to-end approach with learnable pulse shape and nonlinear Volterra equalization but fixed bias and peak-to-peak modulation current. The numerical simulations on the four approaches show that the joint optimization of bias, peak-to-peak current, constellation points, pulse shaping, and equalization outperforms all other approaches throughout the tested symbol rates.

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Linearisation Method of DML-Based Transmitters for Optical Communications Part I: Theory and Simulation Studies

Cited by 4 publications

References 35 publications

Linearisation Method of DML-Based Transmitters for Optical Communications Part III: Pulse Amplitude Modulation

Linearisation Method of DML-Based Transmitters for Optical Communications Part III: Pulse Amplitude Modulation

Linearisation Method of DML-based Transmitters for Optical Communications Part II: Experimental Demonstration and Implementation Methods

End-to-end optimization of optical communication systems based on directly modulated lasers

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