459:, received signals for a PMD system have a much more favourable carrier-to-interference ratio, as the amount of leakage is often much smaller than the useful signal, whereas spatial multiplexing operates with an amount of interference equal to the amount of useful signal. This observation, valid for a good PMD design, allows the adaptive XPIC to be designed in a simpler manner than a general MIMO cancelling scheme, since the starting point (without cancellation) is typically already sufficient for establishing a low-capacity link by means of a reduced modulation.
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As a consequence, the signal at one of the received single-polarization terminals actually contains a dominant quantity of the desired signal (meant to be transmitted onto one polarization) and a minor amount of undesired signal (meant to be transported by the other polarization), which represents an
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A dual-polarized signal thus carries two independent data streams to a receiving antenna, which can itself be a single-polarized one, for receiving only one of the two streams at a time, or a dual-polarized model, again relaying its received signal to two single-polarization output connectors (via an
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When the transmitter has a waveguide interface, typically rectangular in order to be in single-mode region at the operating frequency, a dual-polarized antenna with a circular (or square) waveguide port is the radiating element chosen for modern communication systems. The circular or square waveguide
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Under some circumstances, the data rate of a radio link can be doubled by transmitting two separate channels of radio waves on the same frequency, using orthogonal polarization. For example, in point to point terrestrial microwave links, the transmitting antenna can have two feed antennas; a vertical
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An XPIC typically acts on one of the received signals "C" containing the desired signal as dominant term and uses the other received "X" signal too (containing the interfering signal as dominant term). The XPIC algorithm multiplies the "X" by a complex coefficient and then adds it to the received
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The ideal dual-polarization system lies its foundation onto the perfect orthogonality of the two polarization states, and any of the single-polarized interfaces at the receiver would theoretically contain only the signal meant to be transmitted by the desired polarization, thus introducing no
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interference over the former. As a consequence, each received signal must be cleared of the interference level in order to reach the required signal-to-noise-and-interference ratio (SNIR) needed by the receiving stages, which may be of the order of more than 30 dB for high-level M-
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are the drifts in polarization state that occur continuously over time due to physical changes in the fibre environment. Over a long-distance system, these drifts accumulate progressively without limit, resulting in rapid and erratic rotation of the polarized light's
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port is needed so that at least two degenerate modes are supported. An ad-hoc component must be therefore introduced in such situations to merge two separate single-polarized signals into one dual-polarized physical interface, namely an
411:) within the radio unit itself. Alternatively, the orthomode transducer may be built into the antenna, and allow connection of separate radios, or separate ports of the same radio, to the antenna.
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Some types of outdoor microwave radios have integrated orthomode transducers and operate in both polarities from a single radio unit, performing cross-polarization interference cancellation (
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the OMT at the transmitting side has a finite cross-polarization discrimination (XPD) and thus leaks part of the signals meant to be transmitted in one polarization to the other
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infrastructure, potentially substantially expanding its capacity. Multiple polarization signals can be combined to form new states of polarization, which is known as
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the finite XPD of the receiving antenna acts similarly to the transmitting side and the relative alignment of the two antennas contributes to a loss of system XPD
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with two feed points), and embeds the function of an OMT by means of intrinsically transferring the two excitation signals to the orthogonal polarization states.
362:) to a single-polarization antenna for its standard operation. Although two separate single-polarization antennas can be used for PDM (or two adjacent feeds in a
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In case the transmitter has TEM or quasi-TEM output connections, instead, a dual-polarization antenna often presents separate connections (i.e. a printed square
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is often used instead, (i.e. right- and left-handed), as the sense of circular polarization is not changed by the relative orientation of the antenna in space.
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interference and allowing the two data streams to be multiplexed and demultiplexed transparently without any degradation due to the coexistence with the other.
331:). These two separate channels can be received by vertical and horizontal feed antennas at the receiving station. For satellite communications, orthogonal
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schemes. Such operation is carried out by a cross-polarization-interference cancellation (XPIC), typically implemented as a baseband digital stage.
232:
491:, allowing transmission speeds of 100 Gbit/s or more over a single wavelength. Sets of PDM wavelength signals can then be carried over
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as measured on the recombination. Once the MMSE is improved to the required level, the two terminals can switch to high-order modulations.
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propagation in presence of rain, snow, hail creates depolarization, as part of the two impinging polarizations is leaked to the other
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the finite XPD of the receiving OMT likewise further mixes the signals from the dual-polarized port to the single-polarized ports
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the transmitting antenna has a finite XPD and thus leaks part of its input polarizations to the other radiated polarization state
366:), radiating two independent polarization states can be often easily achieved by means of a single dual-polarization antenna.
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Polarization techniques have long been used in radio transmission to reduce interference between channels, particularly at
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Practical systems, however, suffer from non-ideal behaviors which mix the signals and the polarization states together:
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A dual polarization system comprises usually two independent transmitters, each of which can be connected by means of
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to decode the signal in a way that is resilient to polarization-related signal artifacts. Modulations used include
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CableFree 2+0 XPIC Microwave Link showing OMT and two ODUs connected to H & V polarity ports
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downlinks to double the bandwidth by using two orthogonally polarized
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For this reason, PDM is generally used in conjunction with advanced
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Polarization-division multiplexing is typically used together with
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are other phenomena that can cause problems in PDM systems.
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Companies working on commercial PDM technology include
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Companies working on commercial PDM technology include
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The major problem with the practical use of PDM over
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Differential Cross-Polarized
Wireless Communications
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613:She, Alan; Capasso, Federico (17 May 2016).
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594:Orthogonal frequency-division multiplexing
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615:"Parallel Polarization State Generation"
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295:communication by transmitting separate
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497:parallel polarization state generation
589:Orbital angular momentum multiplexing
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246:Polarization-division multiplexing
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584:Wavelength-division multiplexing
534:techniques, allowing the use of
504:fiber-optic transmission systems
493:wavelength-division multiplexing
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16:Method for multiplexing signals
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525:cross-polarization modulation
303:light beams through the same
517:Polarization mode dispersion
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681:The Road to 100G Networking
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521:polarization-dependent loss
372:ortho-mode transducer (OMT)
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301:right circularly polarized
536:digital signal processing
319:frequencies and beyond.
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140:Statistical multiplexing
329:horizontal polarization
579:Polarization scrambler
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385:OMT if in waveguide).
275:states. It is used in
268:by using waves of two
202:Channel access methods
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394:Siae Microelettronica
333:circular polarization
325:vertical polarization
291:. It is also used in
262:electromagnetic waves
207:Medium access control
706:Radio communications
457:spatial multiplexing
281:satellite television
143:(variable bandwidth)
88:(constant bandwidth)
641:2016NatSR...626019S
260:signals carried on
619:Scientific Reports
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649:10.1038/srep26019
625:. Nature: 26019.
364:reflector antenna
266:carrier frequency
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39:Analog modulation
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160:Dynamic TDMA
119:Polarization
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107: /
85:Circuit mode
23:Multiplexing
487:or optical
293:fiber optic
256:method for
695:Categories
632:1602.04463
600:References
360:microstrip
270:orthogonal
701:Photonics
544:PDM-DQPSK
479:Photonics
356:quasi-TEM
352:stripline
346:(such as
344:TEM lines
340:waveguide
277:microwave
667:27184813
573:See also
567:Infinera
540:PDM-QPSK
358:such as
658:4869035
637:Bibcode
252:) is a
124:Spatial
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563:Huawei
523:. and
398:Huawei
180:SC-FDM
627:arXiv
555:Ciena
311:Radio
185:MC-SS
175:OFDMA
663:PMID
565:and
542:and
465:MMSE
409:XPIC
400:and
299:and
297:left
170:DSSS
165:FHSS
114:SDMA
653:PMC
645:doi
546:.
489:QAM
450:QAM
354:or
350:or
342:or
317:VHF
287:in
250:PDM
129:OAM
109:WDM
105:FDM
100:TDM
74:SSB
64:QAM
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54:FM
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248:(
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