In the early 90's I put together an optically switched, Radio Frequency (RF) over Fiber,
communications system using early release RF over Fiber transceivers and one of the first
available all-optical matrix switches. At that time RF over Fiber was a novel concept that was
just becoming commercially available. It was my challenge to convince the RF engineers that I
worked with to adopt this new optical technology and to overcome the "We've never done it
that way before" syndrome.
Now jump forward 25 years and things are more similar than they are different. Although the
RF over Fiber and all-optical switching technologies have advanced greatly, RF engineers in
many cases still have some reluctance to use fiber optics to solve their RF distribution
challenges due mostly to the lack of familiarity with optical technology. And, I'm still challenged
to convince RF engineers of the multitude of advantages related to using an all-optical switch to
dynamically route their RF signals!
And the benefits of RF over Fiber have never been more compelling. Take satellite ground
stations, as one example, with RF over Fiber and all-optical switching:
By the numbers. Why use optical fiber to distribute RF signals?
- Control rooms can be positioned up to 100 km from antennas
- Data traffic can be highly protected
- Provisioning can be done remotely, automatically, and instantly
OK, I'm convinced that using fiber optics to distribute my RF signals makes sense. What else
do I need?
- Improved distance x bandwidth – With the 0.4 dB/km RF attenuation achieved by optical cables you can send high frequency signals further through fiber (up to 100 km)
than you ever could in copper cables (45 db/km)
- Future-proof signal distribution – Once you install the fiber optic distribution cables and optical switches they never have to be upgraded to handle different signals in the
future. Simply change out the RFoF transceivers and use the same fiber optic backbone
to distribute signals of any format, any frequency, now and into the future
- Improved signal security/TEMPEST – Fiber cables and all-optical switches won’t
conduct your sensitive signals to unintended places and enable you to keep your signals
where they belong, not leaking out for others to intercept
- Lightning immunity – Nonconductive fiber cables won’t carry lightning strikes into your control room
- Reduced cable size, weight and cost – At 1/30 th the weight and ¼ the size of RF cables, fiber cables provide significant deployment advantages, and with reduced cost
- Options for combining many signals onto a single fiber – Optical Wavelength Division
Multiplexing (WDM) allows you to combine up to 80 or more channels onto a single
fiber for even more efficient distribution cabling
In addition to the physical fiber cables or network, you'll need to think about routing traffic. An
all-optical matrix switch, rather than using traditional electrical RF switches, enables true
optimization of RF over Fiber, bringing benefits that include:
- Ultra-low loss – traffic is switched with less than 1 dB insertion loss
- Future proof – any signal frequency, any signal format, now or in the future
- Opex savings – provisioning can be automated, dynamic, and instantaneous
- Ultra-low cross talk – better than 100 dB isolation between channels at any frequency
- No jitter – stable and quiet loss (remember, you cannot use a switch based on MEMS
technology because they cannot meet this critical requirement for RF over Fiber
And you'll need optical and RF cable connectors and RF-to- optical transceivers, and a
multiplexer if you plan to run different channels on a single fiber, and a host of cabling and
cable management products.
That sounds complex, and different. We've never done it that way before. Should I stick with
the old way?
And so we come full circle. But the truth is that it's not that scary and the flexibility, operational
efficiencies, and protection you gain are compelling. In these types of applications, where data
is mission critical, most governments can't afford to lag.
There is a learning curve, but it’s not steep. 25 years ago, when I was building that first RF over
Fiber communication system, I couldn’t have truthfully made that statement.
That's why I can appreciate the commitment Huber+Suhner has made to the RFOF application.
Leveraging the company's core expertise in fiber optics, and making strategic acquisitions, we
can supply best-in-class equipment for an end-to-end optically-switched RFOF complete
solution. If you've been in the trenches, this will sound like a dream come true. But it's true and
certainly achievable today.
I have a long history with RF over Fiber deployments and have only touched on the benefits in
this post. There’s a lot more to share. I'd love to help you think through how your RF
distribution challenges might be addressed.
I can be reached at Mike.Bitting@hubersuhner.com