FMCW LiDAR has many advantages over time-of-flight (ToF) LiDAR, including the ability to measure instantaneous velocity, natural immunity to interference and sunlight, as well as improved long range performance and finer-grained depth resolution. Despite these advantages, it has lagged in popularity compared to its ToF LiDAR cousin through the last decade. This slow adoption is due to several factors such as system complexity and supply chain, but one of the key reasons is data rate. It’s more challenging to build an FMCW LiDAR that delivers as many points per second as leading ToF systems. This is why any LiDAR units you see driving around on top of cars today are ToF, not FMCW. That’s all about to change.

与飞行时间(ToF)LiDAR相比， FMCW LiDAR具有许多优势，包括能够测量瞬时速度，对干扰和日光的自然免疫力以及改进的远程性能和更细粒度的深度分辨率。 尽管具有这些优点，但在过去十年中，与ToF LiDAR表亲相比，它的受欢迎程度有所下降。 这种缓慢的采用是由于诸如系统复杂性和供应链之类的几个因素，但是关键原因之一是数据速率。 构建FMCW LiDAR更具挑战性，该雷达每秒可提供领先的ToF系统多达每秒的点数。 这就是为什么您今天看到的在汽车上方行驶的任何LiDAR装置都是ToF，而不是FMCW。 这一切都将改变。

Data rate is important because the more points per second a sensor can capture, the more information it knows about the world around it. All these points help to resolve objects that are smaller, further away, and faster-moving in order to react quickly and make better informed decisions. Many use cases demand hundreds of thousands to millions of points per second of LiDAR data to accurately identify distant objects, map detailed environments, or make fast decisions in safe, reliable systems.

数据速率很重要，因为传感器每秒可以捕获的点数越多，就可以了解有关其周围环境的更多信息。 所有这些点有助于解决更小，更远且移动速度更快的对象，从而快速做出React并做出更明智的决策。 许多用例需要每秒数十万至数百万个LiDAR数据，才能准确识别远处的物体，绘制详细的环境或在安全可靠的系统中做出快速决策。

Why are high data rates a challenge for FMCW? It comes down to a problem of scalability, which is why the solution lies on a semiconductor wafer, one of the best embodiments of scalability anywhere in the world. A single FMCW LiDAR transceiver is able to deliver only a fraction of the data most use cases require, and each transceiver is typically too costly and too large to make a system with many in parallel that would have a high enough data rate. If you could shrink these components onto a chip you would reduce the size and cost dramatically to the point where a high data rate FMCW LiDAR product would not only be realizable but small and inexpensive enough for widespread adoption across all kinds of industries. This is what we have set out to do at Voyant. Our products are built using silicon photonics to leverage this fundamental scalability advantage.

为什么高数据速率对FMCW构成挑战？ 归结为可扩展性的问题，这就是为什么解决方案位于半导体晶圆上的原因，这是世界上任何地方可扩展性的最佳体现之一。 单个FMCW LiDAR收发器只能提供大多数用例所需数据的一小部分，并且每个收发器通常太昂贵且太大，以致于无法形成具有许多并行系统且具有足够高数据速率的系统。 如果您可以将这些组件缩小到芯片上，则将大大降低尺寸和成本，从而达到高数据速率FMCW LiDAR产品不仅可以实现，而且体积小且价格便宜，可以在各种行业中广泛采用。 这就是我们在Voyant计划要做的。 我们的产品是使用硅光子学构建的，以利用此基本可扩展性优势。

Silicon photonics repurposes the CMOS electronics technology platform to make micro and nano-scale optical circuits for manipulating light. The microscopic components on our chips replace lenses, beamsplitters, and fibers in the same way that transistors replaced vacuum tubes. But this is not for convenience. The ability to put billions of transistors onto a tiny chip that’s affordable and fits inside your phone gives us the power to make systems with far higher performance and sophistication than was even conceivable when there were only millions of transistors, let alone when transistors themselves were several inch long tubes. In the same way, a chip-scale FMCW LiDAR can achieve high performance at a low size and cost that’s entirely unattainable by any discrete systems.

硅光子 技术重新利用CMOS电子技术平台来制造用于操纵光的微米和纳米级光学电路。 我们芯片上的微观部件可以像晶体管取代真空管一样替换透镜，分束器和光纤。 但这不是为了方便。 能够将数十亿个晶体管安装在价格适中并适合您手机内部的微型芯片上，这使我们有能力使系统的性能和复杂性远远超过只有数百万个晶体管时才想到的系统 ，更不用说只有几个晶体管时了英寸长的管子 。 以同样的方式，芯片级FMCW LiDAR可以以小尺寸和低成本实现高性能，这是任何分立系统都无法实现的。

Let’s break this down a bit.

让我们分解一下。

Let’s start with a single FMCW LiDAR transceiver, which is basically a special laser, mixer, and detector. The laser has a narrow linewidth and a continually-modulating frequency. The detector is a moderate-bandwidth photodiode that listens for a beat tone between a local reference and the returned laser light after it has bounced off a distant object. Each LiDAR pixel requires a minimum dwell time in order to detect an object a certain distance away, and a single transceiver is capable of delivering up to 1/dwell time number of points per second. Long distance ranging at 200m or more requires a dwell time of tens of microseconds, which translates to tens of thousands up to maybe 100,000 points per second out of a single FMCW transceiver. That’s pretty far off from where we need to be.

让我们从单个FMCW LiDAR收发器开始，它基本上是一种特殊的激光器， 混频器和检测器。 激光器具有较窄的线宽和连续的调制频率。 该检测器是一个中等带宽的光电二极管，在从远处物体反弹后，它会侦听本地参考和返回的激光之间的拍音。 每个LiDAR像素都需要最短的驻留时间，以便在一定距离外检测到物体，并且单个收发器能够每秒传输多达1个/点的驻留时间 。 200m或更远距离的长距离需要数十微秒的驻留时间，这意味着单个FMCW收发器每秒可以成千上万个，可能高达每秒100,000个点。 这与我们要做的事情相去甚远。

A straightforward solution to boost the data rate is to make a LiDAR unit that transmits and receives multiple beams in parallel. For a goal of around one million points per second we’ll need upwards of 10 to 20 or more parallel FMCW transceivers.

提高数据速率的一种直接解决方案是制造一个可并行发送和接收多个光束的LiDAR单元。 为了实现每秒约一百万点的目标，我们将需要多达10到20个或更多的并行FMCW收发器。

The typical laser/detector pair often dominates the cost of a discrete FMCW system, so using 10 or 20 parallel transceivers actually multiplies the cost of the system many times. The laser/detector pair alone can easily cost hundreds of dollars, with the majority of this cost coming in the expensive package. Diode lasers that may be used for FMCW, as with standard telecom lasers, are traditionally packaged with a fiber in a hermetically sealed gold box butterfly package, which is commonly the main cost driver for datacom transceivers. Putting ten or more of these inside a LiDAR sensor brings the cost of lasers and detectors alone into the thousands of dollars. This is not a big deal for military applications, where FMCW LiDAR has successfully operated for many years, but is a non-starter for almost all commercial applications.

典型的激光/检测器对通常会主导离散FMCW系统的成本，因此使用10或20个并行收发器实际上会使系统的成本成倍增长。 仅激光/探测器对就很容易花费数百美元，其中大部分费用都在昂贵的包装中。 与标准电信激光器一样，可用于FMCW的二极管激光器通常与光纤一起封装在气密的金盒蝶形封装中 ，这通常是数据通信收发器的主要成本驱动因素。 将其中的十个或更多放置在LiDAR传感器中，仅激光器和检测器的成本就高达数千美元。 对于FMCW LiDAR已经成功运行多年的军事应用而言，这并不是什么大问题，但是对于几乎所有商业应用而言，这都不是启动器。

Size is also a key consideration. With each laser/detector pair on the order of 1–2 cm wide, plus amplifiers and associated electronics, a bank of 10–20 transceivers alone is about the length of a shoebox, and that doesn’t even include the rest of the system of fibers, mirrors, lenses, and electronics. Along with cost, the large size of today’s LiDAR products will continue to be a barrier to the widespread adoption of 3D sensors in applications well beyond automotive.

大小也是关键考虑因素。 每对激光/检测器对的宽度约为1-2 cm，再加上放大器和相关的电子设备，仅10-20个收发器组就相当于一个鞋盒的长度，甚至不包括系统的其余部分。纤维，镜子，镜片和电子产品。 随着成本的增长，今天的LiDAR产品的大尺寸将继续成为3D传感器在汽车以外应用中广泛采用的障碍。

This is much like the progression of digital camera technology. The large CCD cameras of the 1990s were useful digital cameras, but it was not until after the CMOS image sensor came along that cameras became entirely ubiquitous throughout our world as they are today.

这很像数码相机技术的进步。 1990年代的大型CCD相机是有用的数码相机，但是直到CMOS图像传感器问世之后，相机才在当今世界上变得无处不在。

The same will be true for LiDAR.

对于LiDAR同样如此。

Scalability is a major strength of silicon photonics as a technology platform, as it supports complex optical circuits packed onto a tiny chip while having little impact on cost or size. One powerful means of chip-level scaling is through multiplexing, or combining multiple signals into a common optical data pipeline to increase data flow. Silicon photonics is well suited for multiplexing parallel data channels together onto a single chip. For chip-scale LiDAR, there is absolutely no need to reinvent the wheel here: multiplexing with silicon photonics is a commonly used, mature technique in datacom applications.

可扩展性是硅光子技术作为技术平台的主要优势，因为它支持封装在微小芯片上的复杂光学电路，而对成本或尺寸的影响很小。 芯片级缩放的一种有效方法是通过多路复用或将多个信号组合到一个公共的光学数据管道中以增加数据流。 硅光子学非常适合将并行数据通道多路复用到单个芯片上。 对于芯片级LiDAR，绝对不需要在这里重新发明轮子：与硅光子复用是数据通信应用中一种常用的成熟技术。

Wavelength-division multiplexing (WDM) multiplies the data throughput of a communications link by transmitting different information using different colors of light through the same waveguides and fiber channels. Other forms of multiplexing can transmit more data by leveraging different independent waveguide modes, spatial locations, or even angular momentum, each of which have multiple channels coexisting with minimal cross-channel interference. These systems are actively used today in both data centers and telecom links, with 4- to 8-channel WDM transceivers already deployed in datacom and upwards of 96 WDM channels carried together through a single telecom fiber. Each flavor of multiplexing leverages its own set of photonic components and strategies, some of which are applicable or adaptable for creating a highly multiplexed high data rate chip-scale LiDAR system.

波分复用 (WDM)通过使用不同颜色的光通过相同的波导和光纤通道传输不同的信息，从而使通信链路的数据吞吐量倍增。 其他形式的多路复用可以通过利用不同的独立波导模式，空间位置甚至角动量来传输更多数据，每个波导模式具有并存的多个通道，而交叉通道的干扰最小。 这些系统如今已在数据中心和电信链路中得到积极使用， 已经在数据通信中部署了4至8通道WDM收发器，并通过一条电信光纤将多达96个WDM信道一起部署 。 每种复用方式都利用其自己的一组光子组件和策略，其中一些可应用于或适用于创建高度复用的高数据速率芯片级LiDAR系统。

In our chip-scale LiDAR systems, lasers and amplifiers are integrated at the chip-level directly onto the silicon photonic chip, where they sit right beside the beam steering and receiver optical circuits. Instead of centimeters, each laser or amplifier chip takes up millimeters or less of space and is attached using a quick passively-aligned die attachment. An entire array of these fits inside the footprint of just one single discrete laser package. By using this approach, the laser and chip attachment together cost less than one tenth that of the traditional large discrete components. The photodiodes are integrated as part of the silicon photonic wafer-scale fabrication process and are extremely compact in size, so the marginal cost of even many dozens of detectors is almost negligible. Beyond the detector, the analog receive chain electronics are implemented in a very small CMOS electronics chip, making both size and cost a non-issue, and once signals are digitized the data rate and processing simply scale with the desired number of points per second for the LiDAR product. Altogether, this makes for a highly scalable system that can easily accommodate 10–20 or more parallel FMCW transceivers in order to deliver upwards of 1 million points per second at a cost and form factor small enough to enable widespread adoption across countless commercial applications.

在我们的芯片级LiDAR系统中，激光器和放大器直接在芯片级集成到硅光子芯片上，在硅光子芯片旁边，它们位于光束控制和接收器光学电路旁边。 每个激光或放大器芯片都占用了几毫米或更小的空间，而不是厘米，而是使用快速无源对准的芯片附件进行附着。 这些器件的整个阵列仅适合一个单独的分立激光器封装的占位面积。 通过使用这种方法，激光和芯片的安装成本不到传统大型分立组件的十分之一。 光电二极管作为硅光子晶圆级制造过程的一部分进行集成，并且尺寸极其紧凑，因此，即使是数十个检测器，其边际成本几乎可以忽略不计。 除了检测器之外，模拟接收链电子器件还采用非常小的CMOS电子器件芯片实现，从而使尺寸和成本均无问题，并且一旦信号数字化，数据速率和处理就可以轻松地以所需的每秒点数扩展LiDAR产品。 总而言之，这构成了一个高度可扩展的系统，该系统可以轻松容纳10–20个或更多的并行FMCW收发器，以每秒提供一百万个点以上的速度，而其成本和尺寸又要足够小，从而可以在无数商业应用中得到广泛采用。

The future is inevitably going to be bristling with 3D active sensing everywhere, and the way to make that a reality is to put 3D sensing onto a chip.

未来不可避免地将到处充满3D主动感测，而使现实成为现实的方法是将3D感测放置到芯片上。

Voyant Photonics is laser focused on making that a reality.

Voyant Photonics致力于实现这一目标。

Interested in hearing more about what we’re up to? Check us out at www.voyantphotonics.com.

有兴趣了解更多关于我们的工作吗？ 请访问我们的网站 www.voyantphotonics.com 。