Tech Briefs Magazine - June 2022 - 35

(2) its protocol has limitations on its secure
data rate and on the distance between
the sender and receiver. The engineers
developed a new approach that
overcomes these barriers and provides
for much higher secure communication
rates with longer distances.
Consider two communicators, Party 1
and Party 2. In this new QI method, Party
1 generates a broadband noise source
and sends a small amount to Party 2, who
encodes the message on that light using
binary phase shift keying. Party 2 then
sends the modulated light through an
amplifier that helps the message bits
overcome transmission losses. The amplifier
injects a very significant amount
of noise - thousands of times stronger
than the message signal strength - that
masks the message from a passive eavesdropper.
Party 1 receives this noisy signal
and combines it with a retained local oscillator
(LO) that they derived from the
broadband noise source. Homodyne reception
allows Party 1 to decode the message
at a low bit error rate, while the
noise from Party 2's amplifier precludes
the eavesdropper from getting that information
because they lack the LO that
Party 1 possesses.
To thwart an active attack from an
eavesdropper, Party 1 employs a multimode
entanglement source in which
they randomly choose to send to Party 2
the signal beam of entangled signal and
idler with the same bandwidth as the
broadband noise source. The idler beam
is sent to a single-photon counter to
monitor and record its photon flux and
detection times. Party 2 taps part of the
incoming light and similarly sends it to
their single-photon counter. Both parties
must maintain desired levels of photon
flux and coincidences in their photon
detection times. An active
eavesdropper who injects their own light
into the communication channel will
necessarily disrupt level of coincidences
between the Parties' photon detection
times and alert them to the active attack.
Some of the key advantages of this
technology are: It uses commercial offthe-shelf
components for easy implementation,
broadband LO can be amplified
to allow long-distance transmission
without degradation, and Homodyne
reception with broadband LO does not
have data bandwidth limitation.
For more information, contact tlo-inquiries@
mit.edu; 617-253-6966.
Materials for Next-Generation LED-Based
Data Communications
Two relatively unexplored semiconducting materials can be used in optical
communications systems.
University of Surrey and University of Cambridge, United Kingdom
L
ight-emitting diode (LED)-based
com munications techniques allow
computing devices, including cellphones,
to communicate with one another
using infrared light. However,
LED techniques are underused because
in its current state, an LED transmits
data at far slower speeds than other
wireless technologies such as
light-fidelity (Li-Fi).
Researchers have demonstrated how
organic semiconductors, colloidal quanEmerging
high-speed LEDs
tum dots (CQDs), and metal halide perovskites
(perovskites) can be used in
LED-based optical communications systems.
The team explored efforts to improve
the performance and efficiency of
these LEDs and they considered their
potential applications in on-chip interconnects
and Li-Fi.
2 Flexible biosensors
1 Self-guiding vehicles
4 Underwater
communications
3 Data center
6 Li-Fi and short-distance on-board communications
5 Low-cost on-chip loT sensors
Organic semiconductors, CQDs, and perovskites are promising materials that could be used in a
number of optoelectronic applications.
Tech Briefs, June 2022
www.techbriefs.com
Although the conventional inorganic
thin-film technologies are likely to continue
to play a dominant role in optical
communications, LEDs based on these
materials can play a complementary role
that could have a sizable impact on the
industry. Future applications of LEDs
will not be limited to the fields of lighting
and displays. The team investigated
deployment of real-world communication
links using the LEDs from the material,
device, and system aspects.
Photonic devices for the Internet of
Things (IoT) and 6G communication
systems need to be high-speed, low-cost,
and easy to integrate. Organic semiconductors,
CQDs, and perovskites are
promising materials that could be used
to complement and/or compete with
conventional inorganic counterparts in
particular optoelectronic applications.
For more information, contact Dr. Wei Zhang
at wz0003@surrey.ac.uk; +44 (0)1483 688707.
35
TB Communications 0622_1.indd 35
Cov
ToC
5/19/22 12:48 PM
1010101

http://www.techbriefs.com http://info.hotims.com/82322-850

Tech Briefs Magazine - June 2022

Table of Contents for the Digital Edition of Tech Briefs Magazine - June 2022