The excitement about fiber-optical products for HDMI at CEDIA was pretty palpable with several firms demonstrating solutions during the show.
This only makes sense as we continue struggling with super high speed data such as 18Gpbs 4K@60 Ultra HD video. So let’s lay down some foundational factors when it comes to running fiber.
Nine times out of 10, fiber’s performance will surpass copper by a huge margin. We have had a wonderful opportunity testing, measuring and learning more about fiber products recently. I do want to mention that copper solutions are also improving — maybe not at the lengths fiber achieves, but certainly longer distances than one would have predicted one year ago.
In the past, basics such as length limitations, gauge requirements, material properties, and even the topology of each individual cable structure had to be thrown into the system environment soup.
By understanding these basic facts, one would be able to determine the type of transmission line to use for each application. For example, you may only want to run short lengths behind a rack of some type so as to have a well-organized and neat cable layout.
Fiber is the same as far as determining the right product for each job, but it is also very different in that both the electrical and mechanical specifications take on new meanings. This subject can go very deep, and we will address it further as it becomes more popular.
You have to pay close attention to not only each attribute within a fiber transmission line but also its cost-to-performance ratio.
In terms of specs, you will need to consider regarding a fiber transmission solution, one of the first things you think you would want to know is bandwidth performance. That makes sense, but as we have learned, factory claims can come back to bite you if you are not careful.
Case in point, we’ve tested quite a few products whose packaging claimed 18Gbps but had a hard time reaching 10.2Gpbs. We’ve also seen fiber products come in exceeding their 18Gbps claim with pretty respectable insertion loss numbers out to 30Gbps aggregate.
Next it is time to decide whether you prefer a hybrid or an all-fiber product. Constructed in the correct form, fiber-and-copper hybrid products can have a little better power management than direct fiber products depending on the design. Should the electronics in the fiber demand a high current, external power is required.
With just fiber, in this case, the product would need to have two separate power supply systems — one for the source and the other for the sink (display). There are even some hybrid products that require two separate power supply systems; it is all in the power management of each device.
On the opposite side of the spectrum there are hybrids that use no external power (which, in most cases, can deplete the HDMI 5-volt line voltage). Power management can become more and more important due to the susceptibility of noise in an 18Gbps system environment.
We have just touched the surface here when it comes to fiber and its operation. We have experienced very good products, and also some very bad ones. Over the next few months we will dive deeper into technical features of the transmission line that will help you learn and make better decisions.
Features such as:
- Fiber Type — OM or OS
- Index — OM 1,2,3, or 4
- OS Index — OS1 OS2 ISP
- Operating Wavelength (λ)
- Transducers — LEDs vs. VCSELs
Under the-jacket-stuff is also important, such as: chromatic dispersion; numerical aperture; bend radius and fiber refraction/reflection (Snell’s Law); and insertion losses, whether by scattering or absorption.
