Showing papers on "Optical Carrier transmission rates published in 2016"

Ultra-High Capacity Indoor Optical Wireless Communication Using 2D-Steered Pencil Beams

Abstract: Free-space indoor optical communication deploying pencil beams can offer ultra-high wireless capacity individually per user device. By means of two-dimensional (2D) diffractive modules, such as a pair of crossed gratings, 2D steering of multiple beams by just tuning the wavelength of each beam can be achieved. The design aspects of an indoor system fed via an intelligent optical fiber backbone network are discussed. 2D angular beam steering over a $\rm{6^\circ \times12^\circ}$ area was achieved by wavelength tuning from 1505 to 1630 nm. System experiments using PAM-4 modulation have shown a capacity of 32 Gbit/s per infrared beam. With radio-over-fiber techniques and optical carrier recovery from the downstream signal, 10 Gbit/s upstream transmission of a 60 GHz radio signal has been shown using adaptive DMT modulation.

Transmission of single lane 128 Gbit/s PAM-4 signals over an 80 km SSMF link, enabled by DDMZM aided dispersion pre-compensation.

Abstract: Direct detection systems with advanced modulation schemes are of great importance in metropolitan networks, because of their low cost and low power requirements. In particular, PAM-4 has attracted considerable attention, but has significant transmission distance limitations in the C-band. To extend its reach, we used a dual drive Mach-Zehnder modulator to generate a chromatic dispersion (CD) pre-compensated signal with an extra (j-1) multiplication to align the optical carrier and the modulated optical signal; by doing so, we achieved successful 128 Gbit/s transmission over an 80 km SSMF link, the longest reported reach of single lane 100 Gbit/s PAM-4 signals over DCF-free links. Synchronized bandwidth pre-compensation was also used, to reduce the influence of bandwidth-limitations.

Single-sideband W-band photonic vector millimeter-wave signal generation by one single I/Q modulator.

Abstract: We propose a new scheme to generate single-sideband (SSB) photonic vector millimeter-wave (mm-wave) signal adopting asymmetrical SSB modulation enabled by a single in-phase/quadrature (I/Q) modulator. The driving signal for the I/Q modulator is generated by software-based digital signal processing (DSP) instead of a complicated transmitter electrical circuit, which significantly simplifies the system architecture and increases system stability. One vector-modulated optical sideband and one unmodulated optical sideband, with different sideband frequencies, located at two sides of a significantly suppressed central optical carrier, are generated by the I/Q modulator and used for heterodyne beating to generate the electrical vector mm-wave signal. The two optical sidebands are robust to fiber dispersion and can be transmitted over relatively long-haul fiber. We experimentally demonstrate the generation and transmission of 4-Gbaud 80-GHz quadrature-phase-shift-keying-modulated (QPSK-modulated) SSB vector mm-wave signal over 240-km single-mode fiber-28 without optical dispersion compensation.

A Full-Duplex Radio-Over-Fiber Link Based on a Dual-Polarization Mach–Zehnder Modulator

Abstract: A simple and low-cost full-duplex radio-over-fiber (RoF) link implementing wavelength reuse for short-range applications is proposed and demonstrated based on a dual-polarization Mach–Zehnder modulator (DPol-MZM). In the center unit, a continuous-wave optical carrier is sent to a DPol-MZM to generate an optical signal with data modulation along one polarization direction and an unmodulated optical carrier along the other orthogonal polarization direction. In the remote antenna unit, a polarization beam splitter is used to separate the modulated signal for downstream service and the unmodulated optical carrier for upstream signal remodulation. A proof-of-concept experiment is carried out. Performance of the established full-duplex RoF link operated at 18 GHz is investigated. The measured bit error rate and the error vector magnitude confirm that the proposed architecture is a promising candidate for future high-speed and low-cost short-range applications.

Optical vector network analyzer based on amplitude-phase modulation

Abstract: The article describes the principles of optical vector network analyzer (OVNA) design for fiber Bragg gratings (FBG) characterization based on amplitude-phase modulation of optical carrier that allow us to improve the measurement accuracy of amplitude and phase parameters of the elements under test. Unlike existing OVNA based on a single-sideband and unbalanced double sideband amplitude modulation, the ratio of the two side components of the probing radiation is used for analysis of amplitude and phase parameters of the tested elements, and the radiation of the optical carrier is suppressed, or the latter is used as a local oscillator. The suggested OVNA is designed for the narrow band-stop elements (π-phaseshift FBG) and wide band-pass elements (linear chirped FBG) research.

Single carrier high symbol rate transmitter for data rates up to 1.0 Tb/s

Abstract: We demonstrate an all-electronically multiplexed, single optical carrier, flexible rate transmitter based on a high-speed 3-bit multiplexer and analog-to-digital converter integrated circuit. Line rates up to 1.08 Tb/s are obtained using 90 Gbd PDM-64QAM.

Photonic Generation of Equivalent Single Sideband Vector Signals for RoF Systems

Abstract: A novel approach for generating RF vector signals with equivalent single sideband (SSB) modulation based on a dual-polarization quadrature phase-shift keying (DP-QPSK) modulator is proposed and experimentally demonstrated. One QPSK modulator in the DP-QPSK modulator is driven by a single-frequency RF signal. By properly setting its biases, a SSB carrier suppressed (SSB-CS) signal is generated. The other QPSK modulator in the DP-QPSK modulator is modulated by I/Q data streams, resulting in a baseband vector signal carried by the optical carrier. A polarizer is placed after the DP-QPSK modulator to combine the two signals with orthogonal polarization, leading to the generation of an equivalent SSB signal, which is free from the dispersion-induced power fading effect. By adjusting the angle of the polarizer, the carrier-to-sideband ratio can also be flexible tuned to maximize the transmission performance. The proposed system is verified by an experiment. The generation of a 1.25-GBd vector signal with QPSK modulation format at 10.5 GHz and the transmission of the signal over 25-km single-mode fiber are evaluated. An error-free transmission is achieved at a received optical power of -12 dBm and the power penalty is <;1 dB. The proposed approach features all-optical and compact configuration.

Phase-coherent orthogonally polarized optical single sideband modulation with arbitrarily tunable optical carrier-to-sideband ratio

Abstract: We propose and experimentally verify a novel approach to achieve phase-coherence orthogonally polarized optical single sideband (OSSB) modulation with a tunable optically carrier-to-sideband ratio (OCSR). In our scheme, the orthogonally polarized OSSB signal is achieved using a dual-polarization quadrature phase shift keying (DP-QPSK) modulator without an optical band-pass filter (OBPF). Therefore, the proposed method is wavelength independent. The DP-QPSK modulator includes two parallel QPSK modulators locating on its two arms. The upper QPSK modulator of the DP-QPSK modulator is driven by two quadrature sinusoidal microwave signals and works at the frequency shifting condition whose bias voltages are optimized to suppress the optical. The lower QPSK modulator of that works at the maximum transmission point and the optical carrier is not modulated. The OCSR is continuously tunable by simply adjusting the bias voltages of the lower modulator. The frequency shifting optical signal from the upper QPSK modulator and the optical carrier from the lower QPSK modulator are combined together at the output of the DP-QPSK modulator. The optical carrier and sideband are polarized orthogonally. The generated OSSB signals could be used to shift and code the phase of the microwave signal and generate ultra-wideband (UWB) microwave pulse. The proposed method is analyzed and experimental demonstrated.

Experimental Demonstration of Bidirectional OFDM/OQAM-MIMO Signal Over a Multicore Fiber System

Abstract: A bidirectional transmission and massive multi-input multi-output (MIMO) enabled radio over a multicore fiber system with centralized optical carrier delivery is experimentally investigated in this paper. Optical carriers for upstream are delivered from the central office to the remote antenna unit via the inner core for the coreless implementation. In our experiment, as one of the fifth-generation (5G) waveform candidates, orthogonal frequency division multiplexing using offset quadrature amplitude modulation (OFDM/OQAM) is adopted in both uplink and downlink to increase the spectral efficiency and side lobes suppression ratio. An advanced $2\times 2$ MIMO-OFDM/OQAM channel estimation algorithm is optimally designed to equalize the hybrid optical and wireless MIMO channels. The experimental results show that bidirectional transmission of 4.46 Gb/s $2\times 2$ MIMO-OFDM/16-OQAM could be achieved over a 20-km seven-core fiber and a 0.4-m wireless link. The proposed scheme proves that the multicore fiber can realize the transparent transmission of bidirectional radio signals and effectively simplify the infrastructures in the future 5G cellular systems.

High-frequency reverse-time chaos generation using an optical matched filter

Abstract: The optical reverse-time chaos is realized by modulating a binary pseudo-random bit sequence onto an optical carrier, and then driving an optical matched filter. The filter is demonstrated experimentally by using two fiber Bragg gratings and a Fourier-domain programmable optical processor. The complexity relationship between the binary input sequence and the output chaos signal is studied. This approach could be a novel way to generate a high speed repeatable and controllable optical chaos signal, which has the potential to be used in optical secure communication systems.

Photonic Generation of Binary and Quaternary Phase-Coded Microwave Waveforms With Frequency Quadrupling

Abstract: A photonic approach to generate a phase-coded microwave waveform with frequency quadrupling is proposed and experimentally demonstrated in this paper. The system consists of a dual-parallel Mach-Zehnder modulator (DPMZM), a phase modulator (PM), a fiber Bragg grating (FBG), an optical coupler, and a photodetector. An optical carrier is modulated by a local oscillator (LO) in the DPMZM, and pure ±second-order sidebands are generated. Then, the two sidebands are separated by the FBG, and one of them is modulated by the coding signal through the PM. Both binary and quaternary phase-coded microwave signals with frequency quadrupling of the LO signal can be generated after detecting the recombined two sidebands. The proposed scheme is verified by experiments; phase-coded microwave waveforms at 24 and 12 GHz are generated by applying 6- and 3-GHz LO signals to the DPMZM, respectively. The pulse compression ratios of the generated waveforms are in good agreement with theoretical value.

Frequency-Sextupling Optoelectronic Oscillator Using a Mach–Zehnder Interferometer and an FBG

Abstract: A frequency-sextupling dual-loop optoelectronic oscillator (OEO) without any electronic microwave filters is proposed and demonstrated. In the proposed OEO, a modulated signal that consists of an optical carrier and odd-order sidebands is generated using a Mach–Zehnder interferometer (MZI). The modulated signal is then divided into reflection components and transmission components by a fiber Bragg grating (FBG). The reflection components, including the optical carrier and the ±1st-order sidebands, are sent to a photodetector (PD1) and then fed back to the MZI to form the OEO loop. The transmission components, including the ±3rd-order sidebands, are sent to another PD (PD2) to generate a frequency-sextupled microwave signal. Meanwhile, a microwave photonic filter is formed by the joint operation of the MZI, the FBG, and an optical domain dual-loop composite cavity that performs the selection of the oscillation mode. As a result, a fundamental oscillation signal at 4.03 GHz and its frequency-sextupled microwave signal at 24.18 GHz are generated with their performance being evaluated.

2 × 2 multiple-input multiple-output optical-wireless integration system based on optical independent-sideband modulation enabled by an in-phase/quadrature modulator.

Abstract: We propose a novel and simple 2×2 multiple-input multiple-output (MIMO) optical-wireless integration system, in which optical independent-sideband modulation enabled by an in-phase/quadrature (I/Q) modulator, instead of optical polarization multiplexing, is used to assist the simultaneous generation of two wireless millimeter-wave (mm-wave) signals. Software-based digital signal processing is used to generate the driving signal for the I/Q modulator, the output of which is two independent single-sideband optical vector signals located at two sides of a large central optical carrier. Based on our proposed 2×2 MIMO optical-wireless integration system, we experimentally demonstrate the simultaneous generation and 2×2 MIMO wireless delivery of two independent 40-GHz quadrature-phase-shift-keying (QPSK) wireless mm-wave signals. Each 40-GHz QPSK wireless mm-wave signal can carry up to 4-Gbaud transmitter data with a bit-error ratio less than the hard-decision forward-error-correction threshold of 3.8×10-3.

System and method for providing optically coded information

Abstract: An active optical machine-readable tag (i.e. optical tag) is provided that is addressable and readable within a line-of-sight of a reader device, such as a mobile device equipped with a camera, at substantially large distances. A method and a system are provided for an active optical tag and a camera-based reader thereof that facilitate asynchronous communication at data rates that are sufficiently high for practical uses, while reducing the flicker associated with the low-frequency optical carrier to a level hardly noticeable by people. The optical tag may be formed as an array of light emitting elements, arranged in a single dimension (linear) or two dimension (planar) arrangement. The array may be embodied as part of a large display unit.

Simple High-Bandwidth Sideband Locking with Heterodyne Readout

Abstract: We present a robust sideband laser locking technique that is ideally suited for applications requiring low probe power and heterodyne readout. By feeding back to a high-bandwidth voltage controlled oscillator, we lock a first-order phase-modulation sideband to a table-top high-finesse Fabry-Perot cavity, achieving a feedback bandwidth of 3.5 MHz with a single integrator, limited fundamentally by the signal delay. The directly measured transfer function of the closed feedback loop agrees with a model assuming ideal system components, and from this we suggest a modified design that should realistically achieve a bandwidth exceeding 6 MHz with a near-causally limited feedback gain of $4\times 10^7$ at 1 kHz. The off-resonance optical carrier is used for alignment-free heterodyne readout, alleviating the need for a second laser or additional optical modulators.

Dual-mode laser diode carrier with orthogonal polarization and single-mode modulation for remote-node heterodyne MMW-RoF.

Abstract: A remote-node heterodyne millimeter-wave radio-over-fiber (MMW-RoF) link was proposed by a dual-mode optical carrier with orthogonal polarizations and single-wavelength modulation, which effectively suppresses the chromatic dispersion and four-wave mixing. For optical wireline transmission, the bit error rate (BER) of a 25-km single-mode fiber (SMF) transmitted baseband 24-Gbit/s 64-QAM OFDM can be improved to 5.9×10−4 with an error vector magnitude (EVM) of 7.1%. Moreover, the beat 35-GHz MMW carrier with a 32-dB carrier-to-noise ratio was generated for wireless transmission. The BER and EVM of passband 8-Gbit/s 16-QAM OFDM at 35-GHz MMW carrier were 3.4×10−3 and 17.1%, respectively, after 25-km SMF and 1.6-m free-space transmissions.

High speed CAN transmission scheme supporting data rate of over 100 Mb/s

Abstract: As the number of electronic components in the car increases, the requirement for the higher data transmission scheme among them is on the sharp rise. The control area network (CAN) has been widely adopted to support the in-car communications needs but the data rate is far below what other schemes such as Ethernet and optical fibers can offer. A new scheme for enhancing the speed of CANs has been proposed, where a carrier modulated signal is introduced on top of the existing CAN signal, whereby the data rate can be enhanced over 100 Mb/s. The proposed scheme is compatible with the existing CAN network and accordingly enables seamless upgrade of the existing network to support high-speed demand using CAN protocol.

Optical single sideband modulation based on a high-order birefringent filter using cascaded Solc-Sagnac and Lyot-Sagnac loops.

Abstract: We propose and experimentally demonstrate a simple and flexible photonic approach to implementing single sideband (SSB) modulation based on optical spectral filtering. The high-order birefringent filter is realized through the cascaded Solc-Sagnac and Lyot-Sagnac loops. By adjusting the rotation angle of the polarization controller (PC), the notch position to remove undesired sidebands changes. The frequency for SSB modulation varies accordingly. The periodical response of the filter spectrum allows both the carrier wavelength and the optical carrier to sideband ratio (OCSR) to be tunable. SSB modulation over a frequency range from 5 to 40 GHz and tunable OCSR ranging from −9.174 to 34.408 dB are obtained. The significant merits of the proposed approach are the simple structure, easy operation, large frequency range, tunable OCSR, and wavelength independence. The approach has potential applications in optimizing the transmission performance of photonic microwave signal processing systems.

Polarization Independent Reflective Modulator

Abstract: An apparatus comprising an optical input configured to receive an optical carrier, an polarization beam splitter configured to forward a first polarized component of the optical carrier along a first light path, and forward a second polarized component of the optical carrier along a second light path, wherein the first polarized component comprises a first polarization that is perpendicular to a second polarization of the second polarized component upon exiting the optical splitter, and an optical modulator coupled to the first light path and the second light path, the modulator configured to modulate the first polarized component of the optical carrier and the second polarized component of the optical carrier.

FTTH and Two-Band RoF Transport Systems Based on an Optical Carrier and Colorless Wavelength Separators

Abstract: A hybrid fiber-to-the-home (FTTH) and radio-over-fiber (RoF) transport system is proposed to transmit one wired signal and two wireless signals simultaneously through an optical lightwave. By properly utilizing the polarization characteristic of a phase-remodulated and polarization-remodulated optical lightwave, the first- and second-order sidebands of the lightwave can be colorlessly separated for optical double- and quadruple-frequency RoF transmissions. Experimental results prove that the independent FTTH and two-band RoF signals can be simultaneously generated and separated by relatively low-frequency radio-frequency devices, optical modulators, and polarization beam splitters. The transmission performances are proven by proper bit error rate (BER) performance and clear eye and constellation diagrams. The interference among the transmitted wired signal and double- and quadruple-frequency RoF signals is acceptable. In this case, the wavelength of the optical carrier can be flexibly assigned, and the frequency of the transmitted wireless signals can be easily adjusted without affecting the functionality of the developed optical fiber transport system. The presented architecture can be flexibly employed to support various types of FTTH and microwave and millimeter-wave over fiber transmissions.

Optical device spectrum response measurement method and measurement device based on double sideband modulation and stimulated Brillouin scattering effect

Abstract: The invention discloses an optical device spectrum response measurement method based on double sideband modulation and stimulated Brillouin scattering effect, comprising steps of dividing an optical carrier wave which is outputted by a light source into two paths, performing frequency-beating in a photoelectric detector by a scanning frequency double sideband signal and a carrier having the frequency shifted after the signal passes through the optical device to be detected, obtaining two radio frequency signals which have two different frequencies and carry spectral response information of the optical device to be detected at the scanning frequency double sideband signal frequency position, using a radio frequency amplitude phase extraction module to respectively extract amplitude phase information of two radio frequency signals to obtain an amplitude-frequency response and a phase frequency response of the optical device to be detected at the optical detection signal frequency, changing the wavelength of the optical detection signal and repeating the above process to obtain the spectral vector response information of the optical device to be detected. The invention also discloses an optical device spectrum response measurement device based on the double sideband modulation. Compared with the prior art, the optical device spectrum response measurement method and measurement device greatly improve the measurement range and the measurement efficiency.

Optical device spectral response measurement method and device

Abstract: The present invention discloses an optical device spectral response measurement method, and belongs to the microwave photon measurement technology field. The method comprises the steps of utilizing a double-sideband phase modulation method and a double-sideband amplitude modulation method to modulate a microwave swept-frequency signal on an optical carrier separately to obtain a double-sideband phase modulation signal and a double-sideband amplitude modulation signal separately; taking the double-sideband phase modulation signal and the double-sideband amplitude modulation signal as the detection signals separately, enabling the detection signals to pass a to-be-measured optical device, then carrying out the beat frequency, transforming the spectral response information of the to-be-measured optical device into an electric domain, and then utilizing an amplitude phase extraction method to extract a transmission function of the to-be-measured optical device; adding and subtracting the transmission functions of the to-be-measured optical device under the two detection signals separately to obtain a broadband transmission function of the to-be-measured optical device. The present invention also discloses an optical device spectral response measurement. The measurement device of the present invention has a wider measurement range, and can work at any wavelength.

Tunable single-passband microwave photonic filter based on Brillouin optical carrier recovery

Abstract: The invention discloses a tunable single-passband microwave photonic filter based on Brillouin optical carrier recovery. The tunable single-passband microwave photonic filter comprises a tunable laser, an optical coupler, a first optical amplifier, a second optical amplifier, a first optical circulator, a second optical circulator, first-section single-mode optical fibers, second-section single-mode optical fibers, a first optical polarization controller, a second optical polarization controller, a Mach-Zehnder modulator, an optical fiber Fabry-Perot filer, an optical isolator, a high-speed photoelectric detector and an electric vector network analyzer, wherein the first-section single-mode optical fibers and the second-section single-mode optical fibers are each wound together in a compound mode. By means of the tunable single-passband microwave photonic filter based on the Brillouin optical carrier recovery, the microwave photonic filter with single-passband frequency responses can be achieved, the wavelength of outgoing light of the tunable laser can be changed, and the broadband of the filtering passband of the microwave photonic filter can be tunable.

Device for measuring frequency response characteristic parameter of light wave component

Abstract: The invention discloses a device for measuring the frequency response characteristic parameter of a light wave component. The device comprises a signal separation unit, a signal processing unit, a multichannel amplitude phase frequency mixing reception unit, an RF test unit and a high-frequency optical carrier wave signal generation unit; and a signal source generates a high-frequency modulated electric microwave signal, the signal separation unit separates the high-frequency modulated electric microwave signal into a reference signal and an input signal, and the reference signals and the input signal are received by the multichannel amplitude phase frequency mixing reception unit. Electric-optical, optical-electrical, optical-optical and electric-electric test functions are integrated in the device, the device is convenient to carry and highly integrated, and the frequency response characteristics of different light wave devices can be tested rapidly and accurately.

Device and method for eliminating photonic microwave self-interference signals

Abstract: The invention discloses a device and a method for eliminating photonic microwave self-interference signals, and belongs to the technical field of microwave photonics. According to the device disclosed by the invention, useful signals received of a receiving antenna, self-interference signals and cancellation signals led out by a transmitting antenna are modulated to an optical carrier outputted by a laser by adopting an electro-optic phase modulator, a left sideband and a right side band of phase modulation optical carrier microwave signals are opposite in phase, right sideband plus optical carrier signals and left sideband plus optical carrier signals are acquired through an optical band-pass filter, and the signals are converted through a photoelectric detector so as to eliminate interference signals. The device disclosed by the invention does not need to carry out DC bias voltage control on the electro-optic phase modulator, so that the system structure is greatly simplified, and the system stability is enhanced. Amplitude and time delay regulation and control in an optical domain are great in bandwidth and high in regulation precision, and restrictions of small bandwidth and low regulation precision of an electronic technology are overcome.

Device and method for realizing microwave frequency conversion by utilizing double-drive DPMZM

Abstract: The invention discloses a device and method for realizing microwave frequency conversion by utilizing a double-drive DPMZM, relates to the technical field of microwaves and the technical field of optical communication, and is mainly used for frequency conversion of a microwave signal. The method comprises a light source, a radio-frequency signal source, an intrinsic signal source, an electric shunt device, a phase shifter, the double-drive DPMZM and a photoelectric detector (as drawing show). Double-sideband modulation of a radio-frequency signal and a single-sideband modulation of an intrinsic signal are respectively realized by utilizing the double-drive DPMZM; an optical carrier of an output signal of the double-drive DPMZM can be inhibited by reasonably setting a parameter; and, a frequency conversion signal can be obtained after the frequency of the output signal of the double-drive DPMZM is beaten through the photoelectric detector. The scheme has relatively high conversion efficiency; and furthermore, the power periodic fading due to optical fibre dispersion in a signal transmission process can be avoided.

Wavelength conversion technique for optical frequency dissemination applications

Abstract: We demonstrate coherent wavelength conversion capable of covering the entire C-band by modulating the incoming optical carrier with a compact Fabry-Perot cavity embedded phase modulator and by optical injection locking a semiconductor laser to a tone of the generated optical frequency comb. The phase noise of the converted optical carrier over 1 THz frequency interval is measured to be -40 dBc/Hz at 10 Hz offset and the frequency stability is better than 2 × 10(-17) level for averaging times >1000 s, making this technique a promising solution for comparisons of state-of-the-art optical clocks over complex fiber networks.

Optical carrier microwave signal dynamic wideband real-time digital demodulation system

Abstract: The invention discloses an optical carrier microwave signal dynamic wideband real-time digital demodulation system. The system comprises a photoelectric conversion module, a receiving channel module, an analog-to-digital conversion module, a real-time demodulation signal processing module and a whole-machine reference and sequence generation control module. The photoelectric conversion module receives optical carrier microwave signals of one fiber laser double-frequency beat wave sensor, converts the signals into electric signals, completes a beat wave process of the fiber laser double-frequency beat wave sensor and outputs radio frequency modulation signals comprising sensing information, the receiving channel module performs frequency conversion filtering amplification processing on the radio frequency modulation signals comprising the sensing information so as to obtain intermediate-frequency signals, the intermediate-frequency signals are then converted into intermediate-frequency digital signals through the analog-to-digital conversion module, then, the real-time demodulation signal processing module processes the intermediate-frequency digital signals in real time, demodulates sensing signals and sends detected physical quantity signals of a demodulation result to a next-stage control processing unit, and the whole-machine reference and sequence generation control module sends reference clock and time sequence generation control signals to the receiving channel module, the analog-to-digital conversion module and the real-time demodulation signal processing module.