Analog radio of fiber link of 2-Gbaud OOK/BPSK radio frequency-orbital angular momentum beam transmission over 19.4 km.

The 5G mobile communication system provides ultrareliable, low-latency communications at up to 10 Gbps. However, the scale and power consumption of 5G is tremendous owing to a large number of antenna drivers required by the massive multiple-input multiple-output technique. The 6G system will require an architectural paradigm shift to resolve this problem.

Reconfigurable beam system for non-line-of-sight free-space optical communication.

In this paper, we propose a reconfigurable beam-shaping system to permit energy-efficient non-line-of-sight (NLOS) free-space optical communication. Light is steered around obstacles blocking the direct communication pathway and reaches a receiver after reflecting off of a diffuse surface. A coherent array optical transmitter (CAO-Tx) is used to spatially shape the wavefront of the light incident on a diffuse surface.

40 Gb/s indoor optical wireless system enabled by a cyclically arranged optical beamsteering receiver.

Indoor optical wireless communication with optical beamsteering capability is currently attracting a lot of attention. One major two-dimensional (2D) optical beamsteering scheme is realized by 2D grating or its active counterpart, which is usually based on a spatial light modulator (SLM). However, there is a fundamental trade-off between the field of view (FoV) and power efficiency due to the inherent feature of gratings.

Steerable pencil beams for multi-Gbps indoor optical wireless communication.

We report a novel optical wireless communication (OWC) system solution that supports multi-Gbps (Gigabit-per-second) capacity for indoors. Narrow beams, termed as pencil beams, are directed to wireless users using a tunable laser and a passive diffractive optical element. This enables a wide coverage of ultra-high-capacity communication links to serve multiple network users simultaneously.

Integrated remotely tunable optical delay line for millimeter-wave beam steering fabricated in an InP generic foundry.

A compact and fabrication-tolerant integrated remotely tunable optical delay line is proposed for millimeter-wave beam steering and is fabricated in an InP generic foundry. The proposed delay line is based on a spectrally cyclic-arrayed waveguide grating feedback loop. Its major features include the tolerant architecture with reduced chip size, and bi-directional operation with simplified remote tuning.

Mode-multiplexed transmission over conventional graded-index multimode fibers.

We present experimental results for combined mode-multiplexed and wavelength multiplexed transmission over conventional graded-index multimode fibers. We use mode-selective photonic lanterns as mode couplers to precisely excite a subset of the modes of the multimode fiber and additionally to compensate for the differential group delay between the excited modes. Spatial mode filters are added to suppress undesired higher order modes.

Cyclic additional optical true time delay for microwave beam steering with spectral filtering.

Optical true time delay (OTTD) is an attractive way to realize microwave beam steering (MBS) due to its inherent features of broadband, low-loss, and compactness. In this Letter, we propose a novel OTTD approach named cyclic additional optical true time delay (CAO-TTD). It applies additional integer delays of the microwave carrier frequency to achieve spectral filtering but without disturbing the spatial filtering (beam steering).

Time domain multiplexed spatial division multiplexing receiver.

A novel time domain multiplexed (TDM) spatial division multiplexing (SDM) receiver which allows for the reception of >1 dual polarization mode with a single coherent receiver, and corresponding 4-port oscilloscope, is experimentally demonstrated. Received by two coherent receivers and respective 4-port oscilloscopes, a 3 mode transmission of 28GBaud QPSK, 8, 16, and 32QAM over 41.7km of few-mode fiber demonstrates the performance of the TDM-SDM receiver with respect to back-to-back.

Toward multi-Gbps indoor optical wireless multicasting system employing passive diffractive optics.

This Letter presents the evaluation and demonstration of an optical free-space (FS) multicasting system for multi-Gigabits-per-second (multi-Gbps) indoor transmission. These simultaneous line-of-sight links are formed by infrared beams and are beam-steered using a passive diffraction grating. The experiment has resulted in error-free links (bit error rate <10(-9) at 2.

Phase modulation parallel optical delay detector for microwave angle-of-arrival measurement with accuracy monitored.

A novel phase modulation parallel optical delay detector is proposed for microwave angle-of-arrival measurement with accuracy monitored by using only one dual-electrode Mach-Zehnder modulator. A theoretical model is built up to analyze the proposed system including measurement accuracy monitoring. The spatial delay measurement is translated into the phase shift between two replicas of a microwave signal.

MIMO equalization with adaptive step size for few-mode fiber transmission systems.

Optical multiple-input multiple-output (MIMO) transmission systems generally employ minimum mean squared error time or frequency domain equalizers. Using an experimental 3-mode dual polarization coherent transmission setup, we show that the convergence time of the MMSE time domain equalizer (TDE) and frequency domain equalizer (FDE) can be reduced by approximately 50% and 30%, respectively. The criterion used to estimate the system convergence time is the time it takes for the MIMO equalizer to reach an average output error which is within a margin of 5% of the average output error after 50,000 symbols.

Field demonstration of mode-division multiplexing upgrade scenarios on commercial networks.

We demonstrate three possible scenarios for upgrading current single-mode transmission networks with high capacity few-mode fiber technology using mode-division multiplexing (MDM). The results were obtained from measurements over a number of field-deployed single-mode fiber links with an additional experimental in-line amplified few-mode fiber link. The results confirm the viability of employing MDM using few-mode fiber technology to gradually replace legacy optical systems.

Synchronized signaling delivery for broadband 60 GHz in-building optical wireless network based on digital frequency division multiplexing and digital Nyquist shaping.

A simple and low-cost synchronized signaling delivery scheme has been proposed for a 60 GHz in-building optical wireless network with 12.7Gbps throughput based on digital frequency division multiplexing and digital Nyquist shaping.

73.7 Tb/s (96 x 3 x 256-Gb/s) mode-division-multiplexed DP-16QAM transmission with inline MM-EDFA.

Transmission of a 73.7 Tb/s (96 x 3 x 256-Gb/s) DP-16QAM mode-division-multiplexed signal over 119 km of few-mode fiber transmission line incorporating an inline multi mode EDFA and a phase plate based mode (de-)multiplexer is demonstrated. Data-aided 6 x 6 MIMO digital signal processing was used to demodulate the signal.

10-Gb/s transmission over 20-km single fiber link using 1-GHz RSOA by discrete multitone with multiple access.

We demonstrate a novel 10.5-Gbit/s transmission scheme over 20-km single fiber link by using a remotely fed 1-GHz reflective semiconductor optical amplifier (RSOA). Discrete multitone (DMT) modulation with adaptive bit-/power-loading is applied to overcome the bandwidth limitation of the RSOA.

Cost optimization of optical in-building networks.

Optical fiber-based in-building network solutions can outperform in the near future copper- and radio-based solutions both regarding performance and costs. POF solutions are maturing, and can already today be cheaper than Cat-5e solutions when ducts are shared with electricity power cabling. We compare the CapEx and OpEx of in-building networks for fiber and Cat-5E solutions.

Power-efficient impulse radio ultrawideband pulse generator based on the linear sum of modified doublet pulses.

We propose a new and power-efficient impulse radio ultawideband (IR-UWB) pulse design concept. The proposed concept is based on a linear sum of modified doublet pulses. The proposed concept is both simulated and experimentally demonstrated.

Record high-speed short-range transmission over 1 mm core diameter POF employing DMT modulation.

We report multigigabit/second transmission capacity in 1 mm core diameter graded index plastic optical fiber (POF) exploiting off-the-shelf low-cost components and discrete multitone (DMT) modulation. Transmission capacities of 10.1 Gbits/s x 15 m and 12.

Mode-selective spatial filtering for increased robustness in a mode group diversity multiplexing link.

We propose a very simple optical method to reduce the cross talk among the channels of a mode group diversity multiplexing (MGDM) link. MGDM is an intensity modulation, direct detection, multiple-input, multiple-output technique that creates independent communication channels over a multimode fiber (MMF). The cross talk among the channels is mitigated electronically.

Near-field intensity pattern at the output of silica-based graded-index multimode fibers under selective excitation with a single-mode fiber.

Selective excitation of graded-index multimode fibers (GI-MMFs) with a single-mode fiber (SMF) has gained increased interest for telecommunication applications. It has been proposed as a way to enhance the transmission bandwidth of GI-MMF links and/or create parallel communication channels over the same GI-MMF. Although the effect of SMF excitation on the transmission bandwidth has been investigated, its impact on the near-field intensity pattern at the output face of the GI-MMF has not been systematically addressed.

All-optical demultiplexing of 640 to 40 Gbits/s using filtered chirp of a semiconductor optical amplifier.

We present a high-capacity ultrafast all-optical time demultiplexer that can be employed to retrieve 40 gigabits/second (Gb/s) base-rate channels from a 640 Gb/s single-polarized signal. The demultiplexer utilizes ultrafast effects of filtered chirp of a semiconductor optical amplifier. Excellent demultiplexing performance is shown at very low switching powers: +8 dBm (640 Gb/s data) and -14 dBm (40 GHz clock).

Optical node with time-space-and-wavelength domain contention resolution, deflection and dropping capability.

We experimentally demonstrate an optical node with time-space-and- wavelength domain contention resolution, deflection and dropping capability. The node is composed of an optical buffer based on an optical crossconnect and a wavelength converter. Although the experimental results are shown at 10 Gbit/s the bitrate can be increased substantially.

Time domain add-drop multiplexing for RZ-DPSK OTDM signals.

We show all-optical time domain add-drop multiplexing for a phase modulated OTDM signal for the first time, to our knowledge. The add-drop multiplexer is constructed of a Kerr shutter consisting of a 375 m long highly nonlinear fiber (HNLF), gamma=20 W(-1)km(-1). Successful time domain add-drop multiplexing is shown for 80 Gb/s RZ-DPSK OTDM signals with a 10 Gb/s base rate.

Asynchronous, self-controlled, all-optical label and payload separator using nonlinear polarization rotation in a semiconductor optical amplifier.

We demonstrate an all-optical label and payload separator based on nonlinear polarization rotation in a semiconductor optical amplifier (SOA). The proposed scheme uses a packet format composed of a label and payload information signal combined with a control signal by using polarization division multiplexing. The control signal is employed to separate the label from the payload signal by exploiting nonlinear polarization rotation in a SOA.

High bit-rate combined FSK/IM modulated optical signal generation by using GCSR tunable laser sources.

We report on the generation of combined FSK/IM modulation format by using GCSR tunable laser sources. FSK modulation, up to 100 Mbit/s, has been achieved by modulating the phase section of a GCSR laser source. We experimentally demonstrate generation of combined FSK/IM modulation at 100Mbit/s and 10 Gbit/s, respectively.