Nav: Home

Carrier-assisted differential detection

February 20, 2020

In the recent decade, various schemes of field recovery with direct detection have been investigated in short-reach optical communications. Since direct detection generally provides only intensity information, until now, signals have been mainly restricted to the single sideband (SSB) modulation format in various proposed intensity-only detection schemes. For such detection schemes, signal-signal beating interference (SSBI) is the dominant limitation. Additionally, compared to the optical spectral efficiency (SE), a high electrical SE is a more dictating factor for short-reach applications. The electrical SE is intrinsically limited for the SSB modulation format because one sideband is unfilled, and half of the electrical SE is lost. Apart from the electrical SE, SSB signals suffer from noise folding due to the square-law detection of the photodiode. Consequently, rather than SSB signals, it is highly desirable to investigate the direct detection of complex-valued double sideband (DSB) signals with field recovery.

In a new paper published in Light: Science & Application, engineers from the Department of Electrical and Electronic Engineering, The University of Melbourne, Australia developed a novel receiver scheme for detecting complex-valued double sideband signals with field recovery, called carrier-assisted differential detection (CADD). Compared with conventional single-sideband (SSB) modulation, the electrical SE is doubled without sacrificing the receiver sensitivity. In addition, no precise optical filters are needed for the CADD receiver, indicating the potential of utilizing low-cost uncooled lasers for the CADD receiver scheme.

The gist of the new scheme lies in adopting an optical interferometer and 90-degree optical hybrid in the receiver which is capable of detecting both inphase and quadrature components of the linear optical field. Furthermore, the higher-order nonlinear product is mitigated by a novel iterative cancellation algorithm (See Figure below). These engineers summarize the operational principle of their receiver:

"CADD possesses two advantages over conventional carrier-less differential detection (CDD) for field recovery: (i) CADD doubles the electrical SE compared to CDD, as CADD recovers the linear signal while CDD needs to recover the 2nd-order signal-to-signal beating term, and (ii) CADD is insensitive to chromatic dispersion, while CDD is not. This is because without a carrier, the field of CDD can reach zero, which makes differential detection impossible for large chromatic dispersion"

"The advantage of CADD over the Kramers-Kronig (KK) receiver in direct detection is analogous to that of homodyne over heterodyne receivers in coherent detection - although CADD requires a larger number of components, it reduces the optoelectronic bandwidth by half. By adopting photonic integration, either in the InP or silicon photonics (SiP) platform, the large component count in CADD will be much mitigated, while the reduced bandwidth of CADD will greatly reduce the overall implementation cost. Compared to coherent homodyne receivers, CADD does not require highly stable and low-linewidth lasers, leading to a more compact and cost-effective solution suitable for short-reach applications such as intra-data interconnects and ultra-high-speed wireless fronthaul networks" they added.

"The receiver architecture opens a new class of direct detection schemes that are scalable to high baud rate and suitable for photonic integration. It would be very useful for short-reach applications such as intra-data interconnects and ultra-high-speed wireless fronthaul networks" the engineers forecast.
-end-
This work was supported by Australian Research Council (ARC) Discovery Projects Under the Grants Nos. DP150101864 and DP190103724.

Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

Related Engineers Articles:

Engineers pre-train AI computers to make them even more powerful
Engineers at CSEM have developed a new machine-learning method that paves the way for artificial intelligence to be used in applications that until now have been deemed too sensitive.
Engineers use electricity to clean up toxic water
Powerful electrochemical process destroys water contaminants, such as pesticides. Wastewater is a significant environment issue.
More ecosystem engineers create stability, preventing extinctions
Biological builders like beavers, elephants, and shipworms re-engineer their environments.
Rice engineers: Make wastewater drinkable again
Delivering water to city dwellers can become far more efficient, according to Rice University researchers who say it should involve a healthy level of recycled wastewater.
Engineers help with water under the bridge and other tough environmental decisions
From energy to water to food, civil engineering projects greatly impact natural resources.
Dartmouth engineers develop new way to know liars' intent
Dartmouth engineering researchers have developed a new approach for detecting a speaker's intent to mislead.
Engineers tap DNA to create 'lifelike' machines
Tapping into the unique nature of DNA, Cornell engineers have created simple machines constructed of biomaterials with properties of living things.
UT engineers develop first method for controlling nanomotors
Engineers at UT Austin develop world's first method for controlling the motion of nanomotors with simple visible light as the stimulus.
Engineers get a grip on slippery surfactants
A Rice University group's innovative surfactant theory removes limitations of a 100-year-old model for interfacial behavior in enhanced oil recovery.
Now you see it: Invisibility material created by UCI engineers
Materials inspired by disappearing Hollywood dinosaurs and real-life shy squid have been invented by UCI engineers, according to new findings in Science this Friday.
More Engineers News and Engineers Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.