Compromised extinction and signal-to-noise ratios of weak-resonant-cavity laser diode transmitter injected by channelized and amplitude squeezed spontaneous-emission

Cheng

et al. 2013

Opt. Express

Self Cite

The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (~1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from -9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6 × 10(-7) when pre-amplifying the OFDM data by 5 dB.

“…(6) into the Eq. (9) [39]. Indeed, the coherent injection-locking facilitates the reduction on noise power at background and relaxation oscillation peak of RIN spectrum.…”

Section: The Injection-locking Performance Of the Long-cavity Colorlementioning

confidence: 99%

Coherently wavelength injection-locking a 600-μm long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF

Cheng

et al. 2013

Opt. Express

Self Cite

“…10 [31]. In previous work [30], the digital data transmission is limited at a bit-rate of 2.5 Gb/s, which requires a broadband and flattened modulation response of the WRC-FPLD-based transmitter. That is, the throughput power of the modulated RF signal cannot be decayed or varied too much within the modulation bandwidth.…”

Section: B Competition Of the Longitudinal Mode Extinction Ratio Betmentioning

confidence: 99%

“…The WRC-FPLD releases the strong cavity effect to reduce one end-face reflectance of the FPLD cavity and effectively facilitates the external feedback injection, which is suitable for establishing the external-cavity mode-locking due to its relatively wider gain spectrum and weaker mode selectivity. Unfortunately, the modulating frequency of such a WRC-FPLD is previously reported to limit at 2.488 Gb/s [30]. Although the broadband modulation with a digital data stream can still be worked effectively by enlarging its throughput power and compensating its decayed frequency slope, such a high-power and slope-compensated microwave amplifier for broadband digital signal is too difficult to be accessed, and the power budget is too high.…”

mentioning

confidence: 99%

Harmonic Mode-Locking of 10-GHz Directly Modulated Weak-Resonant-Cavity Fabry–Perot Laser Diode in Self-Feedback Fiber Ring

Lee

IEEE J. Select. Topics Quantum Electron.

Tsai

et al. 2013

Harmonic mode-locking of a directly modulated weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) at 10 GHz via the self-feedback of a fiber ring is demonstrated. The WRC-FPLD directly modulated at 10 GHz simultaneously functions as the gain medium and the active mode-locker in the self-feedback ring. The competition between the gain-switched lasing mechanism inside the WRC-FPLD and the harmonic modelocking mechanism of the incorporated self-feedback fiber ring is monitored. The enhanced mode-locking force can be achieved at self-feedback ratio of 90% and modulation power of 28 dBm. The evolution of pulsating dynamics is dependent with modulation frequency, which enhances the mode-locking and shortens the pulsewidth at the longitudinal mode spacing. A mode-locking theory is used to simulate the coupled-cavity self-injected WRC-FPLD fiber ring. When the lasing mechanism transfers from intracavity gain-switching to intercavity harmonic mode-locking, the longitudinal mode of the WRC-FPLD is broadened with the mode extinction reduced from maximum to minimum. Due to the transformation from the gain-switching to harmonic mode-locking, the coupled-cavity self-feedback WRC-FPLD fiber ring delivers a pulsewidth of 22 ps, a timing jitter of 153 fs, a pulse extinction ratio of 13.65 dB, and a spectral linewidth of 7.6 nm, by setting the WRC-FPLD bias at three times above threshold (∼60 mA) and the intracavity feedback ratio of 90%.

“…In particular, the RIN induced by the ASE master and the intra-band crosstalk [29] between the up-stream transmitted data and the Rayleigh backscattered ASE signal are two important issues to degrade the transmission performance. A solution has been proposed in previous work to solve these problems by using the semiconductor optical amplifier (SOA) based noise reduction unit [30] to squeeze the ASE noise at local optical network unit (ONU) part, which effectively reduces the RIN and the crosstalk to 4.5 dB and 6.3 dB, respectively [31]. Although the noise induced by the ASE injection master could be minimized by the saturated SOA, the extra SOA in each ONU inevitably raises the complexity and cost of the system.…”

mentioning

confidence: 99%

Effect of Injection Coherence on Noise and Bandwidth of Long-Cavity Colorless Laser Diode for Digital Modulation and Transmission

IEEE J. Quantum Electron.

Lin

et al. 2015

The weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) injection-locked by three master sources with different degrees of coherence and directly modulated by two different digital modulation formats is demonstrated. The injection master coherence shows impact on noise, bandwidth, and modulation performances of the slave WRC-FPLD transmitter. Using the highly coherent master, the injectionlocked WRC-FPLD reduces its relative intensity noise peak at 5 GHz by 18 dB and increases its throughput frequency response by 5 dB. This enables the error-free ON-OFF keying (OOK) transmission at 10 Gb/s with a required receiving power sensitivity of −15 dBm at an error rate of 10 −9 . The eye diagrams simulated from the modified rate equations are also performed to show such improvements. With highly coherent injection-locking, the transmitted error of the WRC-FPLD carried orthogonal frequency division multiplexing (OFDM) data with a modulation bandwidth of 3.1 GHz can be minimized to 1.6 × 10 −13 . In comparison, the master-to-slave injectionlocked WPC-FPLD with partial coherence can also provide an 8-Gb/s OOK transmission with a receiving power sensitivity of −19 dBm at bit-error-rate (BER) of 10 9 . Such a cost-effective colorless source also supports a 16-quadrature-amplitude modulation OFDM transmission at 12.5 Gb/s with a BER of 5.6 × 10 −12 to serve multichannel application in next generation passive optical network.Index Terms-Modulation, injection-locked, coherence, semiconductor lasers, dense wavelength division multiplexed passive optical network (DWDM-PON).