Telecom And Datacom, O-bands And The Netherlands
By John Oncea, Editor
Telecom and datacom both move information, one over long distances and the other over shorter distances. Here, we look at how the two vital cogs of the communications ecosystem come into play with O-bands and the greening of data centers.
Quick. What’s the difference between telecom and datacom? Well, The Content Authority writes, “Telecom, short for telecommunications, refers to the transmission of information over long distances. This includes phone calls, video conferencing, and internet connectivity. On the other hand, datacom, short for data communications, refers to the transmission of information over short distances. This includes local area networks (LANs), wide area networks (WANs), and other types of computer networks.”
So, there it is. End of story, right? No, they pay me by the word so let’s take a look at a couple of ways these two technologies play in the photonics sandbox.*
* I recently had a colleague from another office visit ours and asked why he was here. “To play in your sandbox,” he said. “Well,” I said. “Watch out for the turds.” It was only after seeing the weird look on his face that I realized I was thinking of litter boxes instead of sandboxes. Sigh.
O-band: Worst Boy Band Name Ever Or Overlooked Optical Wavelength?
With advancements in fiber optic networks, longer distances, higher speeds, and wavelength-division multiplexing (WDM) have become possible. As a result, fibers are now being utilized in new wavelength ranges, commonly referred to as bands, which allow for more efficient operations of fiber and transmission equipment.
“Singlemode fiber transmission began in the O-band, just above the cutoff wavelength of the SM fiber developed to take advantage of the lower loss of the glass fiber at longer wavelengths and availability of 1310 nm diode lasers,” writes The Fiber Optic Network Association. “Originally, SM fibers were developed for 850 nm lasers where the fiber core was about half what it is for today's conventional SM fiber (~5 microns as opposed to ~8-9 microns at 1310 nm).”
O-bands, writes FiberLabs Inc., were originally considered the primary telecommunication wavelength band used for optical communication in the mid-1970s due to the following two reasons:
- Optical fibers in the mid-1970s exhibited the lowest attenuation near the O-band, not in the C-band. This was early in the development of the optical fiber manufacturing technique and water (OH group) impurities remained in the silica glass matrix. This impurity resulted in an absorption band peaking at 1383 nm, and the tail of this absorption band increased the attenuation in the C-band.
- Silica glass has a zero-material dispersion wavelength in the O-band, and thus it was expected that signal distortion – arising from fiber chromatic dispersion – would be minimized.
Optical fiber manufacturing technology has now matured, allowing for the almost complete elimination of impurities. As a result, the lowest attenuation wavelength has shifted to the C-band. Despite this, the O-band is still widely used in optical communication, primarily due to the zero-dispersion exhibited by the standard telecom optical fiber (ITU-T G.652) in the O-band.
One of the applications of the O-band is for high-speed Ethernet transmission, such as IEEE 100GBASE-LR4 or 400GBASE-LR8. “Small fiber dispersion in the O-band enables high-speed optical transmission without dispersion compensation schemes, such as dispersion-compensation fibers and digital-coherent detection,” FiberLabs writes. “An optical communication system with no dispersion-compensation scheme offers advantages in both the initial investment (lower transceiver price) and operation cost (lower power consumption); both are key requirements for a data center where high-speed Ethernet is heavily used.”
A photonic chip for datacom or telecom is made up of semiconductor layered materials that create a Photonic Integrated Circuit (PIC). According to SMART Phonics, it can turn on and off (I/O) and generates and detects photons (light). These photons are utilized to transfer information in the form of on/off data bits using either intensity-modulation direct-detection (IMDD) or intensity/phase (coherent modulation scheme). This means that on/off data is placed on both the time domain/phase and intensity and is processed in the electrical domain.
“Due to its zero chromatic dispersion, providing a capability for high-speed optical transmission rates, the O-band is commonly used in short reach/cost-sensitive markets, Passive-Optical Networks (PONs), and high-speed Ethernet transmission,” writes SMART Phonics. “Currently, the O-band is the primary choice for optical channels in the current and next-generation Data Center Networking (into the data centers), where there is a high-volume demand.”
Peering into a crystal ball, SMART Phonics sees two main demands for the O-band:
- Last mile telecommunications/passive optical network market: The last or the first part (depending on which way you look at it) of a network as it reaches the end user’s premises. In this case, fiber to the x (FTTx) or broadband networks that use optical fiber in the local loop.
- High-capacity data center networking: In an increasingly cloud-based world where content, applications, and data are housed in data centers, it’s critical to optimize the speed and efficiency of connections inside the data centers – or data center networking (DCN). O-band has an important role to play in 800G – 800 million bits per second over multiple or ideally a single optical channel or wavelength – and paving the way to Tb (1.6T/1600G).
Keeping It Green In The Netherlands
Jakajima, organizer and host of Photonics Applications Week, 6th Edition, ** writes the datacom and telecom ecosystems are where more photonics technology is applied than any other. “Photonics provides the bandwidth, speed, reach, and flexibility needed to cope with the growing demand for data processing,” Jakajima writes. “And it does so at much lower energy costs, decreasing the carbon footprint of the internet. As such photonics is the enabling technology for all future wireless and wired broadband technologies.”
Because of this, Jakajima refers to photonics as the savior of data centers. “In 2017 data centers used 3% of the world’s total electricity, a number expected to double every four years. Data centers are faced with the double challenge to increase their processing speed while reducing energy demand. Photonics addresses both problems at once. It can support internet speeds of 200 Terabytes per second. And since photonic chips don’t require cooling, they lower energy use compared to current silicon-based datacenter infrastructure.”
Netherlands Enterprise Agency (NEA), a supporter of entrepreneurs, NGOs, knowledge institutes, policymakers, and organizations, concurs. “The downside of a highly digitizing society is, among others, the high energy consumption of data centers which is increasingly becoming a bottleneck,” writes EEA. “One of the solution perspectives mentioned for this is to increasingly use photonics for data transmission.”
In its report Near term Photonic applications in Datacom and Telecom with impact on reducing energy demand, NEA asks if applications like what Jakajima is promoting are market ready. They answer their question, writing, “The research presented here shows that the urgency is great, that fiber networks already reach deep into the data centers, but that the application of photonics in the servers themselves is still in its infancy.
“The photonic chips that should make a difference are still too expensive and unproven for large-scale adoption by data centers. Waiting for the price curve to go down will lead to the loss of the initiative in the design and production of these photonic chips as well as a delay in making our strained data infrastructure more energy efficient.”
That said, all is not lost. “Technological development in co-packaged and integrated photonics is progressing well,” writes NEA. “Perhaps faster than initially anticipated. This will definitely have a great impact on datacom and telecom energy efficiency.”
** Coming this November to Eindhoven, The Netherlands!