Influence of pseudorandom bit format on the direct modulation performance of semiconductor lasers

Ahmed, Moustafa; Mahmoud, Safwat W. Z.; Mahmoud, Alaa

doi:10.1007/s12043-012-0349-7

Cited by 13 publications

(11 citation statements)

References 12 publications

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“…The increase in I m results in an increase in the intensity of both overshoots of the relaxation oscillations and the level of the ‘1’ bits, which then enlarges the blue shift. The increase in chirp is rather small in the low range of I m < I th within which t setting < T b and the population inversion in each bit reaches its steady‐state value. Therefore, the small increase in I m results in a rather small increase in the population inversion on the transition between ‘0’ and ‘1’ states, which induces a rather small increase in the frequency chirp.…”

Section: Resultsmentioning

confidence: 95%

Comparative study on modulation dynamic characteristics of laser diodes using RZ and NRZ bit formats

Ahmed

Mahmoud

2013

Int J Numerical Modelling

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SUMMARY A comprehensive study on semiconductor laser characteristics under gigabit‐per‐second digital modulation is presented. Comparison of the modulation characteristics under both formats of the return to zero (RZ) and non‐return to zero (NRZ) bit formats is introduced. The modulation characteristics include the eye diagram, turn‐on jitter (TOJ) and frequency chirp. The study elucidates how the laser modulation performance changes with variation of the modulation bit rate relative to the maximum bit rate and the setting bit rate of the relaxation oscillations. The relative contributions of the intrinsic noise of the laser and the pseudorandom bit‐pattern effect to the modulation characteristics are differentiated. The results showed that when the bit rate is higher than the setting bit rate, the eye diagram is partially closed and becomes completely closed when the bit rate increases beyond the maximum bit rate. When the bit rate is higher than 2.25 Gbps, the TOJ values under NRZ modulation are smaller than those under RZ modulation near the threshold level. Under both RZ and NRZ formats, chirp increases with the bit rate with the chirp under the RZ format being higher than that under the NRZ format. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 95%

Comparative study on modulation dynamic characteristics of laser diodes using RZ and NRZ bit formats

Ahmed

Mahmoud

2013

Int J Numerical Modelling

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“…5(b) and (c) plots the simulated eye diagrams at the values of L f-disp . The eye diagrams exhibit resolved paths to rise to the "1" level or to fall to the "0" level, which is an enhanced pseudorandom bit pattern effect [12]. These results indicate that the combined effect of fiber dispersion and frequency chirp on the transmitted laser signal is influenced by the pseudorandom bit pattern effect depending on the history of the "0" bits preceding each "0" bit.…”

Section: Influence Of Fiber Attenuationmentioning

confidence: 81%

“…The thick horizontal borders of both the "1" and "0" levels of the eye diagrams are manifestation of laser and receiver noises. The pudge on top of the eye diagrams are due to the bitpattern effect raised because the bit slot T b is shorter than the setting time of the relaxation oscillations [12]. ii.…”

Section: Influence Of Fiber Attenuationmentioning

confidence: 99%

“…Liang et al [11] showed that in high speed optical transmission systems, the RZ format has better transmission performance than the NRZ format. Detailed comparison of the digital modulation of semiconductor lasers and the fiber system performance under NRZ and RZ modulation are given in [8,12]. It is of practical interest to evaluate the performance of high-speed fiber systems under these formats of direct modulation.…”

Section: Introductionmentioning

confidence: 99%

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Performance evaluation of 40 Gb/s directly-modulated optical fiber communication systems

Albeladi

Ahmed

Bakry

2013

2013 Saudi International Electronics, Communications and Photonics Conference

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This paper introduces simulation of performance evaluation of 40 Gb/s optical fiber communication systems using directly modulated high-speed distributed feedback (DFB) lasers. Electrical signals of return to zero (RZ) and non-return to zero (NRZ) formats with 2 10 -1 pseudorandom bit sequences are used to modulate the laser. A standard single-mode fibers (SSMF) is used. The laser has a blue shift of the lasing frequency and frequency chirps of 65 and 78 GHz under RZ and NRZ formats, which limit the fiber length to 2.51 and 1.37 km. Comparison of the results with those obtained by using a positive non-zero dispersion-shifted fiber (+D-NZDSF) is presented.

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“…The settling time is the time when the error in the output is within 1-5% of the steady state. When the maximum modulation bit rate of the laser is shorter than the setting time of the relaxation oscillation, a bit-pattern effect occurs, and the laser modulation performance is degraded [29]. This limits the application of OIL lasers in practical applications.…”

Section: Modulation Performance Improvementmentioning

confidence: 99%

Modulation Performance Enhancement of Directly Modulated Injection-Locked Semiconductor Lasers Using an Equivalent Electrical Circuit

2021

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We propose an equivalent electrical circuit model to evaluate the direct modulation performance of optically injection-locked (OIL) semiconductor lasers. We modeled the equivalent circuit of the OIL laser based on alternating complex envelope representations, simulated it using the Simulation Program with Integrated Circuit Emphasis (SPICE), and analyzed the frequency response of the OIL laser. Although the frequency response of the OIL laser is better than that of a free-running laser, its 3-dB modulation performance is degraded by the relaxation oscillation that occurs during direct modulation of the semiconductor laser. To overcome this limitation and maintain the maximum modulation performance within the entire locking range, we also designed an electrical filter to preprocess the electrical modulation signal and compensate for the non-flat modulation output of the OIL laser. The damping ratio of the directly modulated OIL laser increased by 0.101 (280%) and its settling time decreased by >0.037 (44%) when the electrical compensation circuit was added, exhibiting a flat 3-dB modulation bandwidth of 28.79 GHz.

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Influence of pseudorandom bit format on the direct modulation performance of semiconductor lasers

Cited by 13 publications

References 12 publications

Comparative study on modulation dynamic characteristics of laser diodes using RZ and NRZ bit formats

Comparative study on modulation dynamic characteristics of laser diodes using RZ and NRZ bit formats

Performance evaluation of 40 Gb/s directly-modulated optical fiber communication systems

Modulation Performance Enhancement of Directly Modulated Injection-Locked Semiconductor Lasers Using an Equivalent Electrical Circuit

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