Showing papers in "IEEE Photonics Technology Letters in 2023"

Corrections to “Improved Perturbation Detection in Direct Detected φ-OTDR Systems Using Matched Filtering”

Abstract: In the above letter [1], the second author’s affiliation was listed incorrectly. The correct affiliation is as follows: Javier Tejedor is with the Institute of Technology, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28668 Boadilla del Monte, Spain (e-mail: javier.tejedornoguerales@ceu.es).

Orbital Angular Momentum Multiplexing Holography for Data Storage

Abstract: In the letter, we propose a holographic data storage method based on orbital angular momentum (OAM). In the proposed method, the OAM holography by discovering strong OAM selectivity in the spatial-frequency domain without a theoretical helical mode index limit is used to label different data pages. Each data page’s points and intensity levels are used to store the information. The data page can be reconstructed by using an OAM reading beam with an inverse helical mode illuminating the OAM-recording hologram. To further increase the density, different OAM-recording holograms are multiplexed. The experimental results show that we can store and read out the data by using the OAM hologram, and the density can be greatly improved by using the OAM-multiplexing hologram.

Single-Mode High-Speed 1550 nm Wafer Fused VCSELs for Narrow WDM Systems

Abstract: High power single-mode wafer fused 1550 nm VCSELs with an active region based on InGaAs quantum wells are fabricated. An InP-based optical cavity and two AlGaAs/GaAs distributed Bragg reflector heterostructures were grown by molecular-beam epita oy. The current and optical confinements are provided by a lateral-structured buried tunnel junction with $\sim ~6~\mu \text{m}$ diameter and etching depth of ~ 20 nm. The VCSELs demonstrate ~ 3.4 mW single-mode continuous-wave output optical power and a threshold current about 2 mA at 20°C. The output optical power exceeds 1 mW at 70°C. A −3dB modulation bandwidth > 13 GHz is obtained at 20°C. Non-return-to-zero data transmission under back-to-back condition of ~ 37 Gbps is shown.

Single-Mode High-Speed 1550 nm Wafer Fused VCSELs for Narrow WDM Systems

Abstract: High power single-mode wafer fused 1550 nm VCSELs with an active region based on InGaAs quantum wells are fabricated. An InP-based optical cavity and two AlGaAs/GaAs distributed Bragg reflector heterostructures were grown by molecular-beam epita oy. The current and optical confinements are provided by a lateral-structured buried tunnel junction with $\sim ~6~\mu \text{m}$ diameter and etching depth of ~ 20 nm. The VCSELs demonstrate ~ 3.4 mW single-mode continuous-wave output optical power and a threshold current about 2 mA at 20°C. The output optical power exceeds 1 mW at 70°C. A −3dB modulation bandwidth > 13 GHz is obtained at 20°C. Non-return-to-zero data transmission under back-to-back condition of ~ 37 Gbps is shown.

Image Encryption by Structured Phase Encoding and Its Effectiveness in Turbulent Medium

Abstract: Structured light carrying optical vortices have gained significant attention in information security as they offer high-dimensional orthogonal states for encoding. These states are usually associated with the orbital angular momentum of light. In this letter, we demonstrate a novel method for binary image encryption using structured phase encoding. The structured phase is obtained by multiple lattices of spatially distributed phase singularity points with varying azimuthal indices. It has been shown that data encoding using orthogonal sets of optical vortex modes enable noise-free decryption and provide robustness against atmospheric turbulence in short propagation distance.

Cost-Effective C-Band 50-Gb/s PON Implemented by Using a 2-Bit DAC and Linear Electrical Equalizer

Abstract: We propose and demonstrate a cost-effective C-band 50-Gb/s downstream 4-ary pulse amplitude modulation passive optical network system implementable by using a 2-bit digital-to-analog converter and a linear electrical equalizer. The waveform distortions induced by band-limitation of opto-electronic devices and fiber chromatic dispersion are compensated by using an electrical and optical pre-equalizers realized by a high-pass filter (HPF) and a dispersion-compensation module (DCM), respectively. To facilitate easy operation and management of the system, the amounts of pre-equalization are all fixed regardless of transmission distance up to 20 km. At the receiver, a linear feed-forward equalizer is employed to compensate for the remaining waveform distortions adaptively to transmission distance. Also, a semiconductor optical amplifier (SOA) is used as an optical pre-amplifier to increase the power budget. We determine the system parameters through experiment to maximize the power budget of the system. The experimental results show that the proposed system is capable of securing the power budget of 29.2 dB.

Amplification of Nanosecond Pulses in a Single- Mode Erbium-Doped Fluoride Fibre Amplifier

Abstract: We investigate the amplification of nanosecond pulses in a single-mode Er-fluoride fibre amplifier. A PPLN-based optical parametric oscillator (OPO) with a Q-switched Nd:YAG pump laser was used to generate seed pulses at a wavelength of 2790 nm. The OPO system produced seed pulses with sub-10 ns pulse durations and pulse energies of $0.5~\mu \text{J}$ at a repetition rate of 10 kHz. These seed pulses were amplified in a single-mode Erbium-fluoride fibre amplifier, consisting of 2.2 m of double-clad fibre with a doping concentration of 7 mol%. Using this setup, we demonstrate gain values of up to 20 dB, output pulse energies of $52.7~\mu \text{J}$ , and peak powers of more than 8 kW.

Beyond 300 Gbps Short-Reach Links Using TFLN MZMs With 500 mV_pp and Linear Equalization

Abstract: Driven by the growing data demand and the stringent power constraints on short-reach datacenter interconnects (DCI), this work compares the driver-less (RF driver-free) transmission performance of thin-film lithium niobate (TFLN) Mach-Zehnder modulators (MZM). Two C-band MZMs (18 / 23 mm) fabricated in a commercial foundry are considered. Using the longer MZM with only linear equalization and ~500 mVpp driving signal, we transmit: (1) 132 Gbaud PAM6 signal (net 309 Gbps) below the 6.7% overhead (OH) hard-decision (HD)-FEC threshold; and (2) 136 Gbaud PAM8 signal (net 342 Gbps) above the 19.02% OH soft-decision (SD)-FEC normalized generalized mutual information (NGMI) threshold of 0.8798 over 500 m of standard single-mode fiber (SSMF). This work demonstrates the feasibility of operating beyond 300 G/lane using TFLN MZMs with CMOS-compatible driving levels.

Amplification of Nanosecond Pulses in a Single- Mode Erbium-Doped Fluoride Fibre Amplifier

Abstract: We investigate the amplification of nanosecond pulses in a single-mode Er-fluoride fibre amplifier. A PPLN-based optical parametric oscillator (OPO) with a Q-switched Nd:YAG pump laser was used to generate seed pulses at a wavelength of 2790 nm. The OPO system produced seed pulses with sub-10 ns pulse durations and pulse energies of $0.5~\mu \text{J}$ at a repetition rate of 10 kHz. These seed pulses were amplified in a single-mode Erbium-fluoride fibre amplifier, consisting of 2.2 m of double-clad fibre with a doping concentration of 7 mol%. Using this setup, we demonstrate gain values of up to 20 dB, output pulse energies of $52.7~\mu \text{J}$ , and peak powers of more than 8 kW.

Cost-Effective C-Band 50-Gb/s PON Implemented by Using a 2-Bit DAC and Linear Electrical Equalizer

Abstract: We propose and demonstrate a cost-effective C-band 50-Gb/s downstream 4-ary pulse amplitude modulation passive optical network system implementable by using a 2-bit digital-to-analog converter and a linear electrical equalizer. The waveform distortions induced by band-limitation of opto-electronic devices and fiber chromatic dispersion are compensated by using an electrical and optical pre-equalizers realized by a high-pass filter (HPF) and a dispersion-compensation module (DCM), respectively. To facilitate easy operation and management of the system, the amounts of pre-equalization are all fixed regardless of transmission distance up to 20 km. At the receiver, a linear feed-forward equalizer is employed to compensate for the remaining waveform distortions adaptively to transmission distance. Also, a semiconductor optical amplifier (SOA) is used as an optical pre-amplifier to increase the power budget. We determine the system parameters through experiment to maximize the power budget of the system. The experimental results show that the proposed system is capable of securing the power budget of 29.2 dB.

Hyperbolic Metamaterial-Based Optical Biosensor for Detecting Cancer Cells

Abstract: Study was made of a hyperbolic metamaterial (HMM)-based optical biosensor in view of possible usage to detect early-stage cancerous cells. The effective medium theory was used to determine the constitutive properties of the metasurface. The reflectance was obtained under different conditions to observe shifts in spectral minima, thereby determining the status of the measurand. The sensitivity and figure-of-merit (FoM) of the structure were evaluated. Observations revealed the device showing relatively high FoM, which depends on the thickness of the HMM and sensing medium, and also, the radius of nanoholes (in HMM) and the angle of incidence of light waves.

Beyond 300 Gbps Short-Reach Links Using TFLN MZMs With 500 mVpp and Linear Equalization

Abstract: Driven by the growing data demand and the stringent power constraints on short-reach datacenter interconnects (DCI), this work compares the driver-less (RF driver-free) transmission performance of thin-film lithium niobate (TFLN) Mach-Zehnder modulators (MZM). Two C-band MZMs (18 / 23 mm) fabricated in a commercial foundry are considered. Using the longer MZM with only linear equalization and ~500 mVpp driving signal, we transmit: (1) 132 Gbaud PAM6 signal (net 309 Gbps) below the 6.7% overhead (OH) hard-decision (HD)-FEC threshold; and (2) 136 Gbaud PAM8 signal (net 342 Gbps) above the 19.02% OH soft-decision (SD)-FEC normalized generalized mutual information (NGMI) threshold of 0.8798 over 500 m of standard single-mode fiber (SSMF). This work demonstrates the feasibility of operating beyond 300 G/lane using TFLN MZMs with CMOS-compatible driving levels.

Hyperbolic Metamaterial-Based Optical Biosensor for Detecting Cancer Cells

Abstract: Study was made of a hyperbolic metamaterial (HMM)-based optical biosensor in view of possible usage to detect early-stage cancerous cells. The effective medium theory was used to determine the constitutive properties of the metasurface. The reflectance was obtained under different conditions to observe shifts in spectral minima, thereby determining the status of the measurand. The sensitivity and figure-of-merit (FoM) of the structure were evaluated. Observations revealed the device showing relatively high FoM, which depends on the thickness of the HMM and sensing medium, and also, the radius of nanoholes (in HMM) and the angle of incidence of light waves.

Optical Filter-Less Photonic FMCW Radar for Multi-Target Detection

Abstract: Frequency modulated continuous wave (FMCW) radar monitors the instantaneous frequency difference between the transmitted and the received signal to determine the time of flight which is proportional to the range. Modern radar system necessitates multispectral sensing to enhance detection capability and anti-jamming efficacy that encourages the evolution from conventional electrical solutions to photonics-enhanced solutions. Photonics offers wide-bandwidth signal generation, parallel processing, and low propagation distortion. Most photonic-assisted radar models are based on optical filters to select the reference and reflected waveform to mix at the photodiode, which limits the system functionality due to the inability to operate in different frequency bands. We propose an optical filter-less photonics-based de-chirp processing of frequency-modulated continuous-wave radar waveforms that overcomes the issue of carrier frequency tunability and agility. A theoretical analysis is performed, followed by simulation, and validated by experiment. The proposed model is experimentally tested for detecting targets at different distances ranging from 150 cm to 210 cm. The system is emulated to detect multiple targets (up to four), showing a range resolution of <15 cm, and signal processing enables the estimation of the widths of different sizes of the targets.

Joint Estimation of Linear and Nonlinear Coherent Optical Fiber Signal-to-Noise Ratio

Abstract: This letter proposes an estimator based on the neural network (NN) to jointly estimate the linear and nonlinear signal-to-noise ratios. The proposed NN-based estimator utilizes new input features based on the entropy extracted from the received signal. Moreover, the computational complexity of the proposed estimator is analyzed. The dataset utilized for training and testing is constructed from dual-polarization 16-ary quadrature amplitude modulation format over different system configurations of the standard single-mode fiber, such as launch power, transmission distances, and the number of wavelength division multiplexed channels. Numerical results reveal the superiority of the proposed NN-based estimator in terms of accuracy and computational complexity compared to the existing NN-based estimators in the literature.

Real-Valued Neural Network Nonlinear Equalization for Long-Reach PONs Based on SSB Modulation

Abstract: Real-valued neural network nonlinear equalization for complex-valued signals combined with single sideband (SSB) modulation is proposed to be a promising scheme for long-reach passive optical networks (LR-PONs). With the assist of neural network equalizer (NNE), fiber nonlinearity induced by large launch power can be mitigated. We experimentally demonstrate a transmission of 120 Gbps 16-QAM SSB signal in C-band over an 80-km single mode fiber (SMF) without optical inline amplifier and pre-amplifier.

A Novel PAPR Reduction Scheme Based on Joint Traditional Algorithm and Machine Learning for CO-OFDM Systems

Abstract: The high peak-to-average power ratio (PAPR) deteriorates the performance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Machine learning (ML) has evolved into a powerful technology to reduce PAPR with its flexible learning ability. We propose a joint scheme which adopts iterative partial transmission sequence (IPTS) scheme cascading a feedforward neural network (FNN) trained on iterative $\pmb {\mu }$ -law companding and filtering (IMCF) algorithm. The proposed scheme greatly reduces the complexity of partial transmission sequence (PTS) scheme, which has excellent PAPR reduction effect and BER performance. Our method achieves a 5.03 dB PAPR reduction for $10\pmb {^{-4}}\,\,\pmb {CCDF}$ and an additional transmission distance of 200 km SMF for $10\pmb {^{-3}}\,\,\pmb {BER}$ , compared with the original OFDM signal. Meanwhile, the computational complexity of proposed scheme is reduced by 32.4%, compared with IPTS cascading IMCF (IPTS-IMCF) scheme.

High Sensitivity Refractometer Based on Tapering Two-Mode Fiber Embedded Long-Period Fiber Grating

Abstract: A novel tapered two-mode fiber embedded long-period fiber grating (TTMF-LPFG) sensor is proposed. The long-period fiber grating (LPFG) is fabricated by periodically splicing the two-mode fiber (TMF) and single-mode fiber (SMF), and then the LPFG is tapered to make a refractive index (RI) sensor. By comparing the sensors with different waist diameters, we found that the smaller the diameter of the sensor is, the higher the sensitivity is. When the taper waist diameter is 36 $\mu \text{m}$ , the maximum sensitivity reaches 1360.43 nm/RIU. TTMF-LPFG shows low sensitivity to the temperature, avoiding the influence of temperature. For the traditional taper fiber, a very thin taper waist is required to excite strong evanescent field (EF) in order to obtain a large RI sensitivity. This situation creates a sensor fragile. For our structure, through the taper, LPFG can be formed and the sensitivity can be improved at the same time. The sensor has great potential in chemical composition analysis and biomedical applications.

300-Gb/s/λ IM/DD Transmission Using Integrated SiP OTDM Transmitter

Abstract: We fabricate an integrated silicon-photonic (SiP) 2-channel optical-time-division-multiplexing (OTDM) transmitter, which is operable with a sinusoidally modulated input light source. This SiP transmitter consists of two Mach-Zehnder modulators (MZMs), two $1 \times 2$ multimode interferometer (MMI) couplers, a time-delay line (TDL), and a thermo-optic phase shifter (TOPS). The 3-dB bandwidth of these MZMs is measured to be as large as 60 GHz. However, due to the limited bandwidths of the various components used in our experiment, the overall bandwidth of each OTDM channel is reduced to $\sim $ 35 GHz. Nevertheless, by using this SiP transmitter, we could demonstrate the transmission of a 300-Gb/s OTDM pulse-amplitude modulation 8-level (PAM8) signal over 500 m of the standard single-mode fiber (SSMF). We also confirm that the fabricated SiP OTDM transmitter can be utilized even with the fabrication fluctuations of the TDL.

Unipolar X-Transform OFDM With Index Modulation for Underwater Optical Wireless Communications

Abstract: This letter presents a novel unipolar scheme called X-transform optical orthogonal frequency division multiplexing with index modulation (XO-OFDM-IM) for underwater optical wireless communication (UOWC). Unlike the conventional schemes, each modulated data in XO-OFDM-IM is transmitted via one or two subcarriers; and the information bits carried by the index of subcarriers are used to produce positive and real time-domain signal without the need for adding direct current (DC) bias or clipping processes. The performance of the proposed scheme has been evaluated via a 2-meter measured UOWC channel to validate its outperformance against its benchmarks. For instance, our scheme offers up to 7 dB improvement in term of signal to noise ratio at a target bit error rate (BER) of 10−4 and up to 8 dB in term of peak-to-average power ratio (PAPR) compared to its counterpart asymmetrically clipped O-OFDM (ACO-OFDM) when considering the same spectral efficiency (SE).

A Scalable 26 GHz RoF Relay System Using Optoelectronic Extender

Abstract: This letter presents data transmission over a 26 GHz millimeter-wave (mmW) radio signal and its coverage extension in an indoor environment using the radio-over-fiber (RoF) technology. The proposed system consists of two RoF seamless wireless links to emulate a mobile fronthaul using a transparent RoF relay link to overcome higher attenuation of the mmW signal. The system is experimentally evaluated for up to 64-quadrature amplitude modulation (QAM), showing the possibility of signal transmission over up to 20 km of optical fiber in the first Section transmission scheme without the usage of an optical amplifier. For the system with 20 km and 30 m long RoF links as well as 4 m and 1 m long relays with no optical amplification, the minimal experimentally measured error vector magnitude is as low as 5% for 64-QAM. Further, a self-developed integrable optoelectronic extender is used for the relay RoF system to simplify the antenna site and keep its footprint small. Moreover, the proposed setup is extended using an optical amplifier toward a scalable scheme with up to 75 km of optical fiber and 5 m long free space optical link.

Influence of the Surface Modification on Carrier Kinetics and ASE of Evaporated Perovskite Film

Abstract: All inorganic cesium lead halide perovskite has emerged as promising optical gain materials due to its excellent optical properties. Carrier recombination and amplified spontaneous emissions (ASE) threshold affect their performance on lasing applications. Herein, CsPbBr3 films were prepared using thermally evaporated method with uniform and high coverage surface. Ammonium salt (PABr) was used to further modify the film. The modified sample exhibited flattened surface morphology, enhanced light-emission, suppressed trap-assisted recombination and Auger recombination, thus improving the efficiency of radiation recombination. It was found that the PABr modified CsPbBr3 exhibit an ASE threshold of 25.45 uJ cm−2 which is lower than that of pure CsPbBr3 with 31.5 uJ cm−2. This work suggest that the thermally evaporated method interfacial modification could provide an effective strategy to ameliorate the room-temperature stimulated emission of CsPbBr3.

All-Polarization-Maintained Microwave Photonic Phase Detector Based on Dual-Polarization Dual-Drive Mach-Zehnder Modulator

Abstract: An all-polarization-maintained microwave photonic phase detector (MPPD) based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DMZM) is demonstrated to detect the phase difference between a microwave signal and an optical pulse train. The robustness of the MPPD can be significantly improved with the all-polarization-maintained structure. A proof-of-concept experiment is carried out. An 8.032-GHz dielectric resonator oscillator (DRO) is locked to an optical pulse train through this MPPD with its phase noise reducing from −109.68 dBc/Hz to −135.41 dBc/Hz at 10-kHz offset frequency. The DP-DMZM-based MPPD shows that the minimum value of the noise floor is around −154 dBc/Hz, and the integrated residual timing jitters from 100 Hz to 100 kHz, 1 MHz, and 3 MHz are 276 as, 696 as, and 2.50 fs, respectively. The MPPD has good stability against external vibrations and stresses.

Spatially Multiplexed Quantum Entropy Source With Single LD for 100-Gbps Random Numbers and Beyond

Abstract: Fast quantum random number (RN) generation is an essential technology for cryptographic applications requiring unpredictable RNs. This letter reports a spatially multiplexed quantum entropy source (QES) with a single laser diode (LD), utilizing parallel homodyne measurement of vacuum fluctuation, for an aggregated RN generation rate of 100 Gbit/s and beyond. The QES uses a high-power distributed feedback LD and a low-loss 1 $\times $ 16 silica planar lightwave circuit splitter and achieves eight-channel parallel operation with a broad bandwidth of 4 GHz each. A four-channel aggregated RN generation rate of 4 $\times $ 25 Gbit/s and further scalability up to $8\times25$ Gbit/s with eight channels are demonstrated via offline post-processing.

Optical Filter-Less Photonic FMCW Radar for Multi-Target Detection

Abstract: Frequency modulated continuous wave (FMCW) radar monitors the instantaneous frequency difference between the transmitted and the received signal to determine the time of flight which is proportional to the range. Modern radar system necessitates multispectral sensing to enhance detection capability and anti-jamming efficacy that encourages the evolution from conventional electrical solutions to photonics-enhanced solutions. Photonics offers wide-bandwidth signal generation, parallel processing, and low propagation distortion. Most photonic-assisted radar models are based on optical filters to select the reference and reflected waveform to mix at the photodiode, which limits the system functionality due to the inability to operate in different frequency bands. We propose an optical filter-less photonics-based de-chirp processing of frequency-modulated continuous-wave radar waveforms that overcomes the issue of carrier frequency tunability and agility. A theoretical analysis is performed, followed by simulation, and validated by experiment. The proposed model is experimentally tested for detecting targets at different distances ranging from 150 cm to 210 cm. The system is emulated to detect multiple targets (up to four), showing a range resolution of <15 cm, and signal processing enables the estimation of the widths of different sizes of the targets.

300-Gb/s/λ IM/DD Transmission Using Integrated SiP OTDM Transmitter

Abstract: We fabricate an integrated silicon-photonic (SiP) 2-channel optical-time-division-multiplexing (OTDM) transmitter, which is operable with a sinusoidally modulated input light source. This SiP transmitter consists of two Mach-Zehnder modulators (MZMs), two 1×2 multimode interferometer (MMI) couplers, a time-delay line (TDL), and a thermo-optic phase shifter (TOPS). The 3-dB bandwidth of these MZMs is measured to be as large as 60 GHz. However, due to the limited bandwidths of the various components used in our experiment, the overall bandwidth of each OTDM channel is reduced to ~35 GHz. Nevertheless, by using this SiP transmitter, we could demonstrate the transmission of a 300-Gb/s OTDM pulse-amplitude modulation 8-level (PAM8) signal over 500 m of the standard single-mode fiber (SSMF). We also confirm that the fabricated SiP OTDM transmitter can be utilized even with the fabrication fluctuations of the TDL.

Bi-Channel Switchable Broadband Terahertz Metamaterial Absorber

Abstract: In this letter, a novel and simple design of switchable broadband terahertz metamaterial absorber is theoretically proposed and numerically demonstrated. The electrically adjusting material of graphene and the temperature-related phase-change material of vanadium dioxide (VO2) are combined in such multi-channel manipulation design. When VO2 is set to be the state of dielectric, the designed platform serves as a broadband absorber with an absorption rate exceeding 90% in the range of 1.31-3.18 THz, and simultaneously the absorption rate can be artificially adjusted from 5.3% to 99.0% at 2.8 THz by adjusting the Fermi energy level of graphene from 0 to 1 eV. When VO2 is set to be the state of metal, the absorber can achieve broadband perfect absorption in the large frequency range of 4.45-8.40 THz. It should be noted that such two broadband absorption windows are remarkably separated in the spectral range, indicating the impressive promise for switching operation during the applications. Due to the symmetry of the structure, the broadband absorber is insensitive to the polarization angle and has good performance in the range of high incidence angle. The design and the findings hold potential applications in the terahertz wave technologies, such as intelligent switching and tunable filtering.

Orbital Angular Momentum Multiplexing Holography for Data Storage

Abstract: In the letter, we propose a holographic data storage method based on orbital angular momentum (OAM). In the proposed method, the OAM holography by discovering strong OAM selectivity in the spatial-frequency domain without a theoretical helical mode index limit is used to label different data pages. Each data page’s points and intensity levels are used to store the information. The data page can be reconstructed by using an OAM reading beam with an inverse helical mode illuminating the OAM-recording hologram. To further increase the density, different OAM-recording holograms are multiplexed. The experimental results show that we can store and read out the data by using the OAM hologram, and the density can be greatly improved by using the OAM-multiplexing hologram.

Real-Time Sub-THz Link Enabled Purely by Optoelectronics: 90–310 GHz Seamless Operation

Abstract: Optoelectronic technology is expected to be the cornerstone of sub-THz communication systems, enabling access to and use of the vast frequency resources found in this portion of the spectrum. In this work we demonstrate a photonics-enabled sub-THz wireless link operating in real-time settings, using a PIN-PD-based THz emitter, and a THz receiver based on an ultra-fast photoconductor. The real-time generation and detection of the information signal is performed by an intermediate frequency (IF) unit based on a commercially available mmWave platform, operating at 1.6 GBaud. The evaluation of our setup takes place on two phases. Firstly, a homodyne scenario is demonstrated, where the same pair of lasers is used at the transmitter and receiver side. Secondly, we demonstrate a heterodyne scheme, employing optical phase locking techniques at the receiver. Error-free operation was achieved in both scenarios at a bit rate of 3.2 Gb/s, over 1 m of free-space with ambient air. The broadband characteristics of our setup were validated, achieving error-free transmission over a 0.22 THz range, spanning from 90 up to 310 GHz. Finally, the stability of our real-time link was successfully demonstrated, showing stable SNR performance at the receiver with adaptive capabilities, over a time period of 5 min and 22 sec.