Aerospace & Defense Technology - June 2022 - 13

Radio Frequency-over-Fiber
radio signals into optical signals using
laser diodes - is not a new concept.
Since its inception over 30 years ago,
RFoF technology has found widespread
adoption in the commercial wireless
communications industry. Seen as a
solution for centralizing wireless network
infrastructure and hedging against
costly infrastructure obsolescence, due
to a rapidly advancing communications
industry, RFoF networks offer a range of
benefits. The networks reduce system
losses, provide immunity to electromagnetic
interference (EMI), reduce system
complexity and integration costs, and
drastically extend the bandwidth-distance
limit of a communication link.
Although adoption of RFoF by militaries
has been slow so far, the time is
right for systems engineers to reevaluate
the potential for optical data links in
next-generation secure communications
infrastructure. Over the last several
decades, the industry has seen significant
advancements in the fabrication
methodologies of glass fibers, optical
connector design, and defense industry
standardization of the manufacture,
assembly, and verification of fiber optic
componentry. This has led to an
increased advocacy for optical network
architecture within modern secure communications
infrastructure deployed in
extreme operating environments.
Denser, Lighter, Stronger Critical
Communications
Further channel density is possible as
optical fibers enable wavelength division
multiplexing (WDM) applications.
Numerous RF communication channels
can be placed on a single optical fiber
by converting each of the signals into
different wavelengths of visible light,
isolating the signals from one another
as they are carried along the fiber (similar
to how a prism works).
Fiber lines are extremely well-aligned
with SWaP-C (Size, Weight, Power and
Cost) initiatives as they are smaller,
lighter, and enable greater transmission
efficiency when compared to coaxial
cable - without sacrificing harsh environment
robustness. Expanded beam
optical connectors enable more resilient
optical connections, reducing the sensitivity
of a link to contamination by dirt,
Aerospace & Defense Technology, June 2022
Radio Frequency-over-Fiber (RFoF) technology.
dust, or damage in the field. Extraordinary
cost savings are possible since optical
fibers in a communication link do
not need to be modified or replaced
when communication parameters
change, and RF-over-Fiber conversion
eliminates the need for costly data processing
at the antenna.
Remaining Future-Ready
Traditional coaxial lines must be optimized
for phase stability and signal
attenuation at the transmit/receive frequency.
Therefore, they must be
replaced when operating frequencies
shift or waveform integrity becomes too
sensitive to losses in the data link. However,
optical fibers are frequency agnostic,
enabling rapid reconfigurability of
an existing communications infrastructure
to optimize the data link for new
operating parameters.
Optical transmission offers a 99%
reduction in signal attenuation per unit
length when compared to large coaxial
lines. This allows for the antenna to be
placed further away from areas of spectral
congestion or mission criticality.
RF-to-optical signal conversion utilizes
direct modulation, seamlessly capturing
the properties of the analog signal when
converting to the optical domain. Once
in the optical domain, the signal can be
transported miles away with near-lossless
efficiency and complete EMI immumobilityengineeringtech.com
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nity. Furthermore, opting for a provider
that can implement direct beam steering
all-optical switching technology
provides near-zero latency connections
that eliminate amplitude distortion of
the RFoF signals. This enables a nearly
invisible switching process in the data
link which is not possible with MEMS
based switching technologies.
The Future of Secure
Communications
Rapid advancements in the state of
the art of laser diode design and photoelectric
conversion technology drive the
continued refinement of the RF-to-optical
conversion process. This enables
even the most phase-critical of RF communications
systems to be reliably converted
to the optical domain for range
extension, data security, a future-ready
system, and rapid reconfigurability of
antenna elements for mission readiness.
The overall performance and cost
potential of RFoF data links in secure
communications topologies implores
RF system engineers to re-evaluate how
next-generation network infrastructure
will be prepared for the future of the
connected battlefield.
This article was written by Mike Teri,
Business Development Manager, A+D Solutions,
Huber+Suhner (Herisau, Switzerland).
For more information, visit http://
info.hotims.com/82322-501.
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http://info.hotims.com/82322-501 http://www.mobilityengineeringtech.com http://info.hotims.com/82322-861
Aerospace & Defense Technology - June 2022

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