Over Bandwidth NRZ Modulation of TO-can Packaged Long-cavity Colorless Laser Diodes with Low Front-facet Reflectance for DWDM-PON Systems
Date Issued
2014
Date
2014
Author(s)
Lin, Shih-Ying
Abstract
In this thesis, the long-cavity colorless laser diodes with different front-facet reflectance are employed to perform the wavelength injection-locked on-off-keying data transmission. By changing front-facet reflectance from 0.2% to 1.2%, the received OOK data improves both signal-to-noise ratio (SNR) and extinction ratio (ER) by 8.0% to enhance the Q factor by 6.3%, which benefits bit-error-rate (BER) reduction by more than two orders of magnitude. As the injection-locking power is raised from -6 to -3 dBm, the receiving power sensitivity of the long-cavity colorless laser diode is improved from -27.9 to -29.2 dBm at BER of 10-9. However, the long-cavity colorless laser diode with a lower front-facet reflectance shows an opposite trend. The injection-locking induced enhancement is limited within a frequency region controlled by the injection power, which results from a large disparity between continuous-wave injection and stimulated emission inside the long-cavity colorless laser diode. Next, a 600-um long-cavity laser diode with 2% low front-facet reflectance is demonstrated as a colorless OC-192 transmitter for the future DWDM-PON, which is packed in a TO-56-can package of only 4-GHz frequency bandwidth but can be over-bandwidth modulated with 10-Gbit/s non-return-to-zero (NRZ) data-stream. The coherent injection-locking successfully suppresses its side-mode intensity and noise floor level, and improves its modulation throughput at higher frequencies. With increasing the coherent injection-locking power from -12 to -3 dBm, the side-mode suppression ratio significantly increases from 39 to 50 dB, which also suppresses the frequency chirp from -12 to -4 GHz within a temporal range of 150 ps. Such an over-bandwidth modulated laser diode still exhibits an on/off extinction ratio of 6.68 dB and a signal-to-noise ratio of 4.96 dB, which can provide a back-to-back receiving power via sensitivity of -12.2 dBm at BER of 10-9. Furthermore, the effect of different front-facet reflectance and injection power are analyzed theoretically based on rate equations. In free-running case, the long-cavity laser diode with a lower front-facet reflectance possesses not only a broader spectrum but a larger modulation bandwidth under a fixed bias current ratio (Ibias/ Ith) operation. Implementing an appropriate amount of injection power, the relaxation resonance frequency and the damping rate can be enhanced owing to the additional coupling of photon density to the phase of the injection -locked laser. In fact, the over-injected and unmodulated photons are unable to create more stimulated emission photons but being noise component in the cavity. By equipping the long-cavity laser diode with temperature control device, the long-cavity colorless laser diode transmitter demonstrates a better transmission performance in WDM-PON system with bit rate of 10 Gbit/s. At back-to-back transmission case, the receiving power sensitivity at BER of 10-9 is -15.4 dBm with ER of 6.95 dB and SNR of 6.18 dB. After 25-km DSF transmission, the receiving power sensitivity slightly degrades to -11.6 dBm at a requested BER of 10-9.
Subjects
光通訊
分波多工光網路
雷射
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R00941043-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):08d849fab9aaece0b44f2985162b5b39