Directly modulated lasers (DML) dominate the short reach optical interconnect market. For years, the bandwidth of commercial DMLs has been limited to a level of 25 GHz, which can support a speed up to around 100 Gb/s via advanced modulations like Nyquist-shaped 4-ary pulse amplitude modulation (PAM-4), carrier-less amplitude phase (CAP) modulation, subcarrier multiplexing, and discrete multitone (DMT). To scale with the capacity evolution of interconnect applications, it is in urgent demand to develop DMLs operated at 50G class and even beyond. In this article, we exploit a newly designed 50G-class short-cavity distributed Bragg reflector (DBR) laser, called the two-κ DBR laser, and demonstrate its capability of supporting 200 Gb/s per wavelength direct modulation and direct detection transmissions. Combining high-speed electronics with the 50G-class DML, we demonstrate a variety of advanced digital modulations including Nyquist-shaped 100-GBaud PAM-4, 80-GBaud PAM-8, and 50-GHz DMT signals, with the maximum net bit rate of 236 Gb/s. The DML exhibits an ultra-low chirp parameter of 1.0, which enables isolator-free operation and dispersion-tolerant transmission over tens of kilometers at O-band.

中文翻译：

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使用高级数字调制对 50 GHz 类激光器进行 200 Gb/s 直接调制

直接调制激光器 (DML) 主导着短距离光互连市场。多年来，商用 DML 的带宽一直被限制在 25 GHz 的水平，它可以通过奈奎斯特形 4 进制脉冲幅度调制 (PAM-4)、载波等高级调制支持高达 100 Gb/s 左右的速度- 低幅度相位 (CAP) 调制、副载波复用和离散多音 (DMT)。为了随着互连应用的容量演进而扩展，迫切需要开发运行在 50G 甚至更高级别的 DML。在本文中，我们开发了一种新设计的 50G 级短腔分布式布拉格反射器 (DBR) 激光器，称为双 κ DBR 激光器，并展示了其支持 200 Gb/s 每波长直接调制和直接检测传输的能力。将高速电子器件与 50G 级 DML 相结合，我们展示了各种高级数字调制，包括奈奎斯特形 100-GBaud PAM-4、80-GBaud PAM-8 和 50-GHz DMT 信号，具有最大净比特236 Gb/s 的速率。DML 具有 1.0 的超低啁啾参数，可在 O 波段实现无隔离器操作和色散耐受传输数十公里。