Photonic Power Solutions
for Communications
Deployments
www.lumentum.com
Application Note
Photonic Power Solutions for Communications Deployments
Introduction
Many applications utilizing remote RF antennas, including digital broadcast TV, mobile cellular
networks, indoor distributed antenna systems, and WiFi and WiMAX networks, rely on local
antennas in electrically noisy, hazardous, or inaccessible locations. These antennas can be
fully supported with dielectric optical fiber for both signal and energy. Analog and digital
signals are commonly routed to and from these antennas through standard optical fiber.
Optical energy for pre-amplifiers or low-power transmitters can also be efficiently delivered
through noise immune and non-conductive optical fiber.
A variety of installation or operational constraints prohibit
optimal location of low-powered communication transceivers,
such as exposure to lightning, exposure to electrically noisy or
high RF emissions, or inaccessibility to grid power. Frequently,
these locations are already outfitted with fiber optic cable. The
fiber optic cable is immune to electrical noise, RF fields, and the
conduction of unexpected electrical currents. A dielectric fiber is
also impervious to lightning discharge, thereby isolating the
transceiver. Figure 1 depicts a method of delivering high optical
power over a Lumentum Photonic Power Module (PPM),
efficiently converting the optical power to electrical energy at
the remote site using a photovoltaic power converter (PPC).
Electrical power
is converted to
light
Laser – Up to 5 W of
light is launched into
the optical fiber
Optical Fiber –
Multimode and single
mode; distances up to
10 km
Remote Device –
Drives electronic
circuitry, biasing of
MEMS and
modulators
+
-
Driver Board – A
support assembly to
drive the laser; easily
configured as a
daughterboard for
placement on the main
printed circuit board
(PCB)
PPC – Converts light
from the optical fiber
into electrical power
+
-
Light is
converted back
to electrical
power
Figure 1. Powering remote electronics using a Lumentum Photonic
Power Module (PPM).
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2
Photonic Power Solutions for Communications Deployments
Lumentum manufactures highly efficient PPMs that transform
optical energy delivered via optical fiber into electrical energy,
powering remote or isolated electronics. These unique modules
consist of a laser diode, a driver, and a PPC that are all connected
using standard optical fiber. These modules enable isolated power
solutions for a wide range of applications, including
communications, power transmission, and medical imaging. PPC
conversion efficiencies approach 45% for voltages up to 12 VDC.
Higher voltages can be achieved using a voltage up converter. A
single power channel can deliver between 0.5 W and 1 W of
electrical power. Output power levels up to 5 W can be achieved
by paralleling power channels.
Communications Applications
Passive RF receiving antennas at remote sites can be electrically
isolated and interfaced to a more conveniently located base
station facility via a single fiber pair at signal frequencies up to
approximately 1 GHz (Figure 2). In this case, the laser diode of
the PPM is located at the accessible base station site. It provides
optical energy to bias a passive lithium niobate modulator at the
remote receive antenna. The incoming RF signal is imposed on
the passive modulator crystal, facilitating relay of the RF signal to
the base station photodiode detector via the optical fiber.
Figure 2. Figure 3. Pre-amplification of a passive, isolated RF receiving antenna
using a Lumentum PPM.
Remotely located and isolated transmit antennas can also be
supported by remote optical fiber. This installation approach
permits transmission of high frequency analog or digital signals
over dielectric optical fiber even if the base station and the
remotely located transmitting antenna are separated by several
kilometers. A Lumentum PPM system supplies up to a few watts
of optical energy via optical fiber to a wavelength-matched PPC
located at the remote transmitter (Figure 4). With an optical-toelectrical conversion efficiency of about 40%, electrical energy
at 3.3 VDC, 5 VDC, or up to 12 VDC is available to power the
signal amplifier in order to feed the transmit antenna. Higher
voltages can be achieved using a voltage up converter. Typically,
the RF modulated signal arrives at the transmit antenna site via
the signal fiber, is detected by a fast photodiode, and is fed to
the amplifier.
Interfacing a passive, isolated RF receiving antenna using a
Lumentum PPM.
For very remote receiving antennas or for RF signal frequencies
above 1 GHz, a pre-amplifier is usually required to boost the
received RF signal strength and to maintain an acceptable
signal-to-noise ratio. In this case, the pre-amplifier can be readily
energized by a Lumentum PPM, consisting of a PPC illuminated
by optical energy supplied from a laser diode located in the base
station over distances of several kilometers (Figure 3). The PPC
easily supplies up to several hundred milliwatts of electrical
energy for pre-amplification. This approach offers total electrical
isolation, excellent noise protection, and a very high receiver
signal-to-noise ratio.
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Figure 4. High frequency signal transmission of an isolated remote
transmit antenna using a Lumentum PPM.
3
GPS receivers in communications applications provide timing
signals for the synchronization of voice and data streams. In
some cases, they also provide stability inputs to a local
frequency source. The antenna/amplifier assembly is mounted to
provide a clear view of the GPS satellite. Traditionally, the GPS
receiver has been located inside the equipment room. Many
recent configurations, though, install the GPS engine remotely
with the antenna/amplifier assembly. In this case, the use of a
PPM eliminates the need for coaxial connections, line amplifiers,
and lightning suppression. The coaxial/power connection is
replaced by an all fiber solution. The laser diode source, mounted
in the indoor equipment bay, provides light transmission over the
fiber that is converted to electrical energy by the PPC in order to
power the outdoor antenna/amplifier assembly (Figure 5). The RF
signal is then optically modulated and transmitted over the same
fiber bundle in digital format to the GPS receiver in the
equipment bay.
Figure 5. Summary
Lumentum PPMs can readily provide the necessary voltage and
current to power picocell transceivers in 3G mobile networks,
WiFi access points, WiMAX base stations, and indoor distributed
antenna systems. GPS receivers, used for timing and
synchronization functions in many communication networks, can
also be powered photonically. PPMs are standard, commercially
available, and highly reliable devices and are capable of providing
up to 12 VDC and hundreds of milliwatts of electrical power
output from a single channel. In addition, multi-channel systems
can provide up to 5 W of electrical power. PPMs have
demonstrated a history of reliable operation in field
environments for over a decade. Non-communication
applications, including driving sensors in HVDC and HVAC power
transmission systems, image amplification in magnetic resonance
imaging (MRI) systems, and powering analog and digital
electronics in nuclear, magnetic, explosive, and similarly
hazardous environments, can also benefit from PPMs.
A GPS timing antenna system using a Lumentum PPM.
North America
Toll Free: 844 810 LITE (5483)
Outside North America
Toll Free: 800 000 LITE (5483)
China
Toll Free: 400 120 LITE (5483)
© 2015 Lumentum Operations LLC
Product specifications and descriptions in this
document are subject to change without notice.
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