Inside Petal: Building the World’s First Petabit-Class Transoceanic Subsea Cable

深入了解 Petal：构建全球首条拍比特级跨洋海底光缆

By Elizabeth Rivera Hartling, Pascal Pecci, Matthew Mitchell 作者：Elizabeth Rivera Hartling, Pascal Pecci, Matthew Mitchell

Petal, the next step in Meta’s subsea innovation, will be the first subsea cable to deliver petabit capacity at transoceanic distances, connecting France and the United States over approximately 7,000 km (4,300 mi). Expected to enter service in 2029, it will be the first subsea cable system to deploy multi-core fiber technology at scale, doubling the capacity per fiber without a proportional increase in power or physical infrastructure. Petal will be built in partnership with NEC and Sumitomo Electric Industries, with support on the French landing from Orange. Petal 是 Meta 海底光缆创新的下一步，它将成为首条在跨洋距离上实现拍比特（petabit）级容量的海底光缆，连接法国和美国，全长约 7,000 公里（4,300 英里）。该系统预计于 2029 年投入使用，将是首个大规模部署多芯光纤技术的海底光缆系统，在不按比例增加电力或物理基础设施的情况下，将每根光纤的容量翻倍。Petal 将与日本电气（NEC）和住友电气工业株式会社合作建设，并获得 Orange 在法国登陆点的支持。

Today, we’re announcing Petal, the first transoceanic subsea cable at petabit capacity, and the first to deploy multi-core fiber at scale. Spanning 7,000 km between France and the United States, Petal will deliver 1 Pbps (1 petabit per second or 1,000 terabits per second), doubling what today’s most advanced subsea cables carry at this distance. That’s roughly the network capacity required for 75% of the world’s population to stream music at the same time.* 今天，我们宣布推出 Petal，这是首条具备拍比特容量的跨洋海底光缆，也是首条大规模部署多芯光纤的光缆。Petal 横跨法国与美国之间 7,000 公里的距离，将提供 1 Pbps（每秒 1 拍比特或每秒 1,000 太比特）的传输速率，是目前最先进海底光缆在同等距离下容量的两倍。这大约相当于全球 75% 的人口同时在线播放音乐所需的网络容量。*

Petal is a key piece of Meta’s subsea cable investments bringing greater capacity, stronger resiliency, and future-proof infrastructure to Europe as demand for communications and reliable connectivity continues to increase. The road to this point has taken years of collaborative engineering with our partners and a complete rethinking of the subsea industry’s approach to cable design. Petal 是 Meta 海底光缆投资的关键组成部分，随着通信和可靠连接需求的持续增长，它将为欧洲带来更大的容量、更强的韧性以及面向未来的基础设施。走到这一步，经历了我们与合作伙伴多年来的工程协作，以及对海底光缆行业设计方法的彻底反思。

Subsea Capacity Innovation

海底容量创新

A subsea cable is the least visible, yet one of the most critical layers of the internet. Approximately 99% of intercontinental data traffic – nearly every message, phone, or video call between continents – travels through glass strands on the ocean floor. Since the introduction of the erbium-doped fiber amplifier (EDFA) in the 1980s, there have been several transformational shifts in subsea cable capacity. 海底光缆是互联网最不显眼但却最关键的层级之一。大约 99% 的洲际数据流量——几乎每一条跨洲的消息、电话或视频通话——都是通过海底的玻璃纤维传输的。自 20 世纪 80 年代掺铒光纤放大器（EDFA）问世以来，海底光缆的容量已经历了几次变革性的飞跃。

In the 2010s, coherent optical transmission technology and dispersion-uncompensated cable designs launched the industry into a decade of dramatic fiber capacity increases of 10x and more until the ever-looming Shannon Limit finally pushed back. To overcome this, the industry pivoted to spatial division multiplexing (SDM) to increase the number of fibers within a subsea cable. Meta scaled its subsea cable approach from Marea’s eight fiber pairs, to Amitié’s 16 fiber pairs, and recently to Anjana’s 24 fiber pairs – the first 0.5 Pbps transatlantic cable system. 在 2010 年代，相干光传输技术和色散非补偿光缆设计推动行业进入了光纤容量增长 10 倍甚至更多的十年，直到日益临近的香农极限（Shannon Limit）最终限制了进一步增长。为了克服这一瓶颈，行业转向空间分复用（SDM）技术，以增加海底光缆内的光纤数量。Meta 将其海底光缆方案从 Marea 的 8 对光纤，扩展到 Amitié 的 16 对光纤，以及最近 Anjana 的 24 对光纤——这是首个 0.5 Pbps 的跨大西洋光缆系统。

Three innovations could double capacity again:

1. Continue on the conventional path to increase the number of fibers to reach 48 fiber pairs.
2. Expand the optical transmission band by using the L-band, as we did with the PLCN cable, resulting in 24 fiber pair C+L transmission.
3. Adopt a 2-core fiber-based solution. 有三种创新可以再次将容量翻倍：
4. 沿用传统路径，增加光纤数量至 48 对。
5. 通过使用 L 波段扩展光传输频带（正如我们在 PLCN 光缆中所做的那样），实现 24 对光纤的 C+L 波段传输。
6. 采用基于双芯光纤的解决方案。

With Petal, we’ve opted for 2-core fiber technology in a 24 fiber-pair system, equivalent to 48 fiber pairs, to make the leap to 1 Pbps at transatlantic distances. This is double Anjana’s capacity and makes Petal the single largest generational increase in cable capacity of any repeatered subsea system, ever. 在 Petal 项目中，我们选择了在 24 对光纤系统中应用双芯光纤技术，这相当于 48 对光纤，从而实现了跨大西洋距离下 1 Pbps 的飞跃。这不仅是 Anjana 容量的两倍，也使 Petal 成为有史以来所有带中继海底光缆系统中，单次代际容量提升幅度最大的一项。

The Challenges of Engineering a 2-Core Fiber Ecosystem

构建双芯光纤生态系统的工程挑战

Carrying a petabit through one cable significantly reduces materials, resources, and carbon footprint compared to building two 0.5 Pbps systems. However, transitioning to a 2-core fiber ecosystem comes with challenges that affect the fiber and subsea repeaters. 与建造两个 0.5 Pbps 的系统相比，通过一根光缆传输拍比特级数据显著减少了材料、资源和碳足迹。然而，向双芯光纤生态系统的转型带来了影响光纤和海底中继器的挑战。

Fiber: Transitioning From Single to 2-Core Fiber

光纤：从单芯向双芯的过渡

There are two main challenges to enabling 2-core fiber for Petal. First is ensuring low attenuation while maintaining the physical dimensions of the outer fiber, including the 125 μm width. Second is minimizing crosstalk between the cores to maximize optical performance and capacity. The former is achieved by using ultra-pure synthetic silica during the manufacture of the preform. The latter is achieved by carefully controlling for high refractive indexes in the cores against lower indexes within the surrounding medium and counter-propagating the optical signals, resulting in nearly immeasurable crosstalk. 1-core fiber allows the industry to counter-propagate traffic using a pair of fibers. Petal’s 2-core fiber will combine this capacity into one fiber strand. 为 Petal 启用双芯光纤面临两大挑战。首先是在保持光纤外径（包括 125 微米宽度）不变的同时确保低衰减。其次是最大限度地减少纤芯之间的串扰，以最大化光学性能和容量。前者通过在制造预制棒时使用超纯合成二氧化硅来实现。后者则通过精确控制纤芯的高折射率与周围介质的低折射率，并使光信号反向传播，从而实现几乎无法测量的串扰。单芯光纤允许行业使用一对光纤进行反向流量传输，而 Petal 的双芯光纤将这种容量整合到了一根光纤中。

Repeater: Amplifying 96 Fiber Cores in a Single Body Repeater

中继器：在单个中继器内放大 96 个纤芯

A 7,000 km subsea cable typically needs about a hundred repeaters to amplify the digital signals along the length of the cable. Petal’s single-body 96 amp repeater uses single-core fiber amplification with a Fan-In/Fan-Out (FIFO) interface to transition 2-core fiber into two single-core fibers within each repeater and then back to 2-core fiber following amplification. This design allows Petal to retain the highest efficiency and reliability of single-core amplification with an SDM pump-sharing architecture. 一条 7,000 公里的海底光缆通常需要约一百个中继器来沿途放大数字信号。Petal 的单体 96 放大器中继器使用单芯光纤放大技术，配合扇入/扇出（FIFO）接口，在每个中继器内将双芯光纤转换为两根单芯光纤，放大后再转回双芯光纤。这种设计使 Petal 能够在采用 SDM 泵浦共享架构的同时，保持单芯放大技术的高效率和高可靠性。

FIFO, combined with highly efficient amplification and high-quality, low-loss fiber, will enable Petal to double capacity without a proportional increase to required power. Petal will remain within existing power feeding equipment limits, rated up to 18 kV, which avoids triggering a requalification of the subsea ecosystem necessary at higher equipment voltages. FIFO 技术结合高效放大和高质量、低损耗光纤，使 Petal 能够在不按比例增加所需功率的情况下将容量翻倍。Petal 将保持在现有供电设备的限制范围内（额定电压高达 18 kV），从而避免了在更高设备电压下对海底生态系统进行重新认证的必要。

The Partnerships Behind Petal

Petal 背后的合作伙伴

Meta’s vision for Petal wouldn’t be possible without the engineering capabilities of our partners at NEC, Sumitomo Electronic Industries, and Orange. NEC, our turnkey system supplier, engineered and qualified the world’s first petabit transoceanic system around the next generation SDM foundation – cable with 2-core fiber, repeaters, FIFO systems, system powering – and is responsible for manufacturing and… 如果没有 NEC、住友电气工业和 Orange 等合作伙伴的工程能力，Meta 实现 Petal 的愿景将是不可能的。作为我们的交钥匙系统供应商，NEC 围绕下一代 SDM 基础——包括双芯光纤光缆、中继器、FIFO 系统和系统供电——设计并验证了全球首个拍比特级跨洋系统，并负责制造和……