Analysis of hybrid mode-locking of two-section quantum dot lasers operating at 1.5 micron

For the first time a detailed study of hybrid mode-locking in two- section InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material. ©2009 Optical Society of America

Combined Linear Block Codes with SLM and PTS to reduce PAPR in OFDM

講到多載波多傳送， 大家就會想到OFDM， 這是一項有很久歷史的技術，最近這項技術越來越受歡迎被用在無線通訊的運用上。 而近來OFDM技術令大家感與趣的主要歸因於數位信號的發展。 由於多載波傳輸中存在著一個缺點即是傳送信號的高PAPR。 我們提出一個觀念去降低OFDM中的PAPR就是利用線性碼中的標準陣列，我們的結構可看成是將SLM及PTS做修改的版本， 在編碼的觀念裡利用降低碼率的方法從陪集首項(coset leaders)中選擇最小的PAPR當做傳送，由於我們把陪集首項當成一般的攪亂(scrambling)動作，因此我們不需要額外傳送外掛資訊(side information)。 在接收端方面可籍由徵狀(syndrom)解碼解回。 最後模擬結果可看我們的提出的方法在降低PAPR也有不錯的效能。Multicarrier transmission, also known as orthogonal frequency division multiplexing(OFDM), is a technique with a long history that has recently seen rising popularity in wireless and wireline applications. One of the major drawbacks of multicarrier transmission is the high peak-to-average power ratio(PAPR) of the transmit signal. We propose a concept to reduce the PAPR in OFDM systems by using the stadard arrays of linear block codes. Our scheme may be regarded as modified versions of the selective mapping(SLM) and Partial Transmit Sequence(PTS), which are to reduce the PAPR by reducing code rate and selecting minimum PAPR from several coset leaders as the transmit signal. Because the coset leaders of a linear code are used for scrambling in our scheme, no side information is required to be transmitted and the received signal can be easily decoded by syndrome decoding. Final our simulation results show that our scheme has good performance in PAPR reduction.1 序論 1 2 系統架構 3 2.1 OFDM介紹. . . . . . . . . . . . . . . . . . . . 3 2.1.1 OFDM訊號發送原理. . . . . . . . . . . . . 3 2.1.2 PAPR問題. . . . . . . . . . . . . . . . . 4 2.2 SLM(selected mapping)系統介紹. . . . . . . . . 5 2.3 PTS(partial transmit sequence)系統介紹. . . . . 8 3 線性碼介紹 11 3.1 標準陣列(Standardarray). . . . . . . . . . . . .11 3.2 里得-米勒碼(Reed-Muller code). . . . . . . . . .12 3.2.1 布林函數. . . . . . . . . . . . . . . . . 12 3.2.2 里得-米勒碼的重要參數. . . . . . . . . . .13 3.3 循環碼(Cyclic code). . . . . . . . . . . . . . .15 3.3.1 循環碼的編碼(Encode). . . . . . . . . . . 15 3.3.2 正交循環碼(Dual Cyclic code). . . . . . . 17 3.3.3 循環碼其它特性. . . . . . . . . . . . . . 18 4 結合循環及SLM系統 19 4.1 SLM選擇序列的產生方法. . . . . . . . . . . . . .19 4.2 模擬方法及結果. . . . . . . . . . . . . . . . . 24 5 結合里得-米勒碼及PTS系統 43 5.1 PTS選擇序列的產生方法. . . . . . . . . . . . . .43 5.2 模擬方法及結果. . . . . . . . . . . . . . . . . 47 6 結論 8

Gain measurements of Fabry-Perot InP/InGaAsP lasers using an ultra high resolution spectrometer

In this paper we present the use of an ultra-high resolution (20 MHz) spectrometer to measure the gain in a Fabry-Pérot InGaAsP laser from subthreshold ASE spectra. The method is derived from the Hakki-Paoli method. A non-linear least-squares fitting of the observed modes is used to extract the gain from the line shape. Each mode of the measured spectrum is fully resolved and fitted separately. Thus the spectral gain curve is not restricted to a parabolic function. The optical gain spectrum and the differential gain are determined. These parameters will be used in our laser simulations

Photonic integrated circuits: where are the limits?

The integration scale in Photonic Integrated Circuits will be pushed to VLSI-level in the coming decade. Key technologies for reduction of device dimensions are high resolution lithography and deep waveguide etching technology. In this paper developments in Photonic Integration are reviewed and the limits for reduction of device dimensions are discussed