高溫優化高速1310奈米直接調變分佈式回饋雷射用於200GbE以上光通訊網路

Abstract

本論文以高溫優化的直接調變1310奈米分佈式回饋雷射 (Distributed Feedback Laser, DFB laser) 為主題，以其在高溫工作環境下保持高速、低噪音雷射作為目標，將透過雷射的直流、光頻譜、高頻小訊號、噪音以及數據傳輸等特性進行量化分析。該雷射具有單一共振腔和簡易蝕刻的 RWG 結構，於25°C和65°C時，它分別保持低閾值電流為6.1 mA和11.7 mA，同時展現出高斜率效率，在25°C時達到0.507 mW/mA，在65°C時達到0.393 mW/mA，確保了於高頻率下的有效調變。該雷射在廣泛的溫度範圍內保持穩定的縱向光譜，SMSR 大於40 dB。它支持高調變頻寬，在25°C時為25.38 GHz，在65°C時為19.44 GHz，促進了高速數據傳輸。該雷射支持 NRZ 的50 Gb/s 的數據傳輸速率和 PAM-4 的35 Gbaud（70 Gb/s），具有低 RIN (<-147.14 dB/Hz)。 本論文分為五個章節，在第一章，本論文會提及在生成式人工智能 (Artificial Intelligence, AI) 以及5G通訊背景下數據中心所處理的數據正以指數級別在增長，而這些需求也連帶著促使光通訊快速成長。除了應對數據中心高密度、低能耗的需求以外，在高溫工作環境下仍保持高速以及低噪音特性也會是不可忽視的條件。因此，如何針對高溫操作環境進行元件優化將會是不可忽視的研究方向；第二章將會介紹半導體雷射基本操作原理，並展示設計高溫優化及高速直接調變DFB雷射時，元件結構以及材料上所需要考量之因素，以及本實驗所設計的雷射結構；第三章會介紹此研究中該直接調變DFB雷射之直流特性量測方法與架設設計，分別為Light-Current-Voltage、光頻譜、接面溫度 (junction temperature) 以及相對強度噪音 (Relative Intensity Noise, RIN) ；第四章則為該直接調變DFB雷射之高頻特性量測方法與架設設計，分別為電光轉換 (Electro-Optics Response) 並透過非歸零 (Non-Return-to-Zero, NRZ) 以及四階脈衝振幅調變 (4-Level Pulse Amplitude Modulation, PAM-4) 之碼型來驗證數據傳輸；第五章則為該研究之總結並結合相關領域之文獻回顧得以勾勒出未來研究之可行方向。

This thesis focuses on the high-temperature optimization of directly modulated 1310 nm distributed feedback lasers. The objective is to maintain high-speed, low-noise laser performance in high-temperature operating environments. A quantitative analysis will be conducted on the direct current, optical spectrum, high-frequency small signal, relative intensity noise, and data transmission characteristics of the laser. The laser features a single resonant cavity and a simply etched ridge waveguide structure, maintaining low threshold currents of 6.1 mA and 11.7 mA at 25°C and 65°C, respectively, while demonstrating high slope efficiencies of 0.507 mW/mA at 25°C and 0.393 mW/mA at 65°C, ensuring effective modulation at high frequencies. The laser exhibits a stable longitudinal spectrum over a wide temperature range with an SMSR greater than 40 dB. It supports high modulation bandwidths of 25.38 GHz at 25°C and 19.44 GHz at 65°C, facilitating high-speed data transmission. The laser supports NRZ data transmission rates of 50 Gb/s and PAM-4 at 35 Gbaud (70 Gb/s) with low RIN (<-147.14 dB/Hz). The thesis is divided into five chapters. In the first chapter, the exponential growth of data processed by data centers driven by generative artificial intelligence (AI) and 5G communications is discussed, highlighting the rapid expansion of optical communications. Meeting the demands for high-density, low-power consumption in data centers, while maintaining high-speed and low-noise performance in high-temperature environments, is an essential consideration. Therefore, optimizing components for high-temperature operation is a crucial research direction. The second chapter introduces the basic operating principles of semiconductor lasers and presents the factors to be considered in the device structure and materials when designing high-temperature optimized and high-speed directly modulated DFB lasers. The laser structure designed in this study is also discussed. The third chapter covers the DC characteristics measurement methods and setup design for the directly modulated DFB laser, including Light-Current-Voltage, optical spectrum, junction temperature, and relative intensity noise (RIN). The fourth chapter describes the high-frequency characteristics measurement methods and setup design for the directly modulated DFB laser, including electro-optic response, and verifies data transmission using Non-Return-to-Zero (NRZ) and 4-Level Pulse Amplitude Modulation (PAM-4) formats. The fifth chapter summarizes the research and integrates a literature review from relevant fields to outline potential future research directions.