Jiun-Yu Sung

Dimming-discrete-multi-tone (DMT) for simultaneous color control and high speed visible light communication

Visible light communication (VLC) using LEDs has attracted significant attention recently for the future secure, license-free and electromagnetic-interference (EMI)-free optical wireless communication. Dimming technique in LED lamp is advantageous for energy efficiency. Color control can be performed in the red-green-blue (RGB) LEDs by using dimming technique. It is highly desirable to employ dimming technique to provide simultaneous color and dimming control and high speed VLC. Here, we proposed and demonstrated a LED dimming control using dimming-discrete-multi-tone (DMT) modulation. High speed DMT-based VLC with simultaneous color and dimming control is demonstrated for the first time to the best of our knowledge. Demonstration and analyses for several modulation conditions and transmission distances are performed, for instance, demonstrating the data rate of 103.5 Mb/s (using RGB LED) with fast Fourier transform (FFT) size of 512.

Compatibility of Silicon Mach-Zehnder Modulators for Advanced Modulation Formats

Silicon photonics which is compatible with mature complementary metal oxide semiconductor (CMOS) fabrication process has been extensively demonstrated for monolithic integration of photonic and electrical circuits. We show that an integrated silicon Mach-Zehnder modulator (MZM) may be used for advanced modulation formats despite the nonlinear dependence of refractive index change with applied voltage in the free-carrier depletion modulator. We experimentally demonstrated the use of a silicon MZM for direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) modulation with advanced data formats of quadrature phase-shift keying (QPSK), 8 phase-shift keying (8PSK) and 16-quadrature amplitude modulation (16-QAM). The measured bit error rate performance of the back-to-back and 50 km single mode fiber transmission of each format is well below the forward error correction limit.

Is blue optical filter necessary in high speed phosphor-based white light LED visible light communications?

Optical blue filter is usually regarded as a critical optical component for high speed phosphor-based white light emitting diode (LED) visible-light-communication (VLC). However, the optical blue filter plays different roles in VLC when using modulations of on-off keying (OOK) or discrete multi-tone (DMT). We show that in the DMT VLC system, the blue optical filter may be unnecessary, and even degrade the transmission performance (by reducing the optical signal-to-noise ratio (SNR)). Analyses and verifications by experiments are performed. To the best of our knowledge, this is the first time the function of blue filters in VLC is explicitly analyzed.

Ring-Based WDM Access Network Providing Both Rayleigh Backscattering Noise Mitigation and Fiber-Fault Protection

In this paper, we propose and investigate a ring-based wavelength-division-multiplexing passive optical network (WDM-PON) providing both Rayleigh backscattering (RB) noise mitigation and fiber-fault protection. The proposed ring-based WDM-PON has a dual-ring architecture to protect and restore any fiber fault. Besides, the ring architecture also can mitigate the RB beat noise, since the RB and the upstream wavelengths are propagating in opposite directions. Here, we discuss and analyze the characteristics of the downstream signals using 10 Gb/s ON-OFF keying (OOK), 10 Gb/s differential phase-shift keying, and 10 Gb/s orthogonal frequency-division multiplexing (OFDM) modulations, respectively. Moreover, we also investigate the upstream traffic using the 2.5 Gb/s OOK and 10 Gb/s OFDM generated by the directly modulated reflective semiconductor optical amplifier-based optical network unit, respectively.

A Convergent Wireline and Wireless Time-and-Wavelength-Division-Multiplexed Passive Optical Network

We propose and demonstrate a convergent wireline and wireless access network using time-and-wavelength-division-multiplexed passive optical network (TWDM-PON) architecture. Bidirectional 40-km single-mode-fiber transmissions (including the 60-GHz wireless transmission) satisfying the forward error correction limit are demonstrated, with data rates of ~10 Gb/s per wavelength in the downstream signal and 17.50 Gb/s per wavelength in the upstream signal. To achieve higher data rate, bit-loading orthogonal frequency-division modulation was used. We also analyze the laser-linewidth-induced performance variation to the signal generated by optical beating and the baseband signal.

TWDM-PON With Signal Remodulation and Rayleigh Noise Circumvention for NG-PON2

We propose and demonstrate a 40-Gb/s (4 × 10 Gb/s) downstream and 10-Gb/s (4 × 2.5 Gb/s) upstream time-wavelength-division-multiplexed passive optical network (TWDM-PON) using signal remodulation. Here, a downstream differential-phase-shift-keying (DPSK) signal and an upstream remodulated carrier-suppressed single-sideband non-return-to-zero (CS-SSB-NRZ) signal are used, which are wavelength shifted to circumvent Rayleigh backscattering (RB). A silicon-based optical microring resonator (MRR) filter is preinstalled at the optical networking unit (ONU) to select the desired downstream wavelength and simultaneously demodulate the downstream DPSK signal, which is then detected by a monolithic-integrated germanium-on-silicon (Ge-Si) photodiode (PD). Using silicon-based devices could be cost effective for the cost-sensitive ONU. The future monolithic integration of a silicon filter, a silicon detector, and a silicon modulator in the ONU is also discussed. The characteristics of the preinstalled silicon-based MRR and the Ge-Si PD are discussed. Error-free transmission (bit-error rate (BER) <;10-9 ) is achieved in both downstream and remodulated upstream signals after propagating through 20 km of standard single-mode fiber (SMF).

Wired and wireless convergent extended-reach optical access network using direct-detection of all-optical OFDM super-channel signal

We propose and demonstrate the feasibility of using all-optical orthogonal frequency division multiplexing (AO-OFDM) for the convergent optical wired and wireless access networks. AO-OFDM relies on all-optically generated orthogonal subcarriers; hence, high data rate (> 100 Gb/s) can be easily achieved without hitting the speed limit of electronic digital-to-analog and analog-to-digital converters (DAC/ADC). A proof-of-concept convergent access network using AO-OFDM super-channel (SC) is demonstrated supporting 40 - 100 Gb/s wired and gigabit/s 100 GHz millimeter-wave (MMW) ROF transmissions.

OFDM RF power-fading circumvention for long-reach WDM-PON

We propose and demonstrate an orthogonal frequency division multiplexing (OFDM) radio-frequency (RF) power-fading circumvention scheme for long-reach wavelength-division-multiplexed passive-optical-network (LR-WDM-PON); hence the same capacity of 40 Gb/s can be provided to all the optical-networking-units (ONUs) in the LR-WDM-PON. Numerical analysis and proof-of-concept experiment are performed.

Measurement of Organic Chemical Refractive Indexes Using an Optical Time-Domain Reflectometer

In this investigation, we propose and experimentally demonstrate a method for measuring the refractive index (RI) of liquid organic chemicals. The scheme is based on a single-mode fiber (SMF) sensor and an optical time-domain reflectometer (OTDR). Here, due to the different reflectance (R) between the SMF and organic liquid chemicals, the reflected power level of the backscattering light (BSL) measured by the OTDR would be different. Therefore, we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate, with stable detected signals, and has the potential to be a valuable tool for use in biological and chemical applications.

A practical in-home illumination consideration to reduce data rate fluctuation in visible light communication

Visible light communication based on LED has attracted more and more attention. As the primary function of LED luminaries is optimized for lighting and illumination, it challenges the communication properties of VLC. An investigation based on different in-home illumination conditions using commercially available whitelight LED luminaries to optimize both illumination and communication is highly desirable. In this work, we investigate joint illumination and communication systems to provide an in-home lighting and VLC system. We first focus on the performance constraints set by illumination properties and discuss lighting conditions using different kinds of commercially available luminaries, beam angles, and LED lamp arrangements, and consider reflections off different wall materials. Then we propose and experimentally demonstrate a white-light phosphor-based LED adaptive data rate VLC system. Finally, the achievable data rates of a joint illumination and VLC system are discussed based on the experimental results, and an environment with reduced VLC data rate fluctuation can be achieved.