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Based on the use of a dual-wavelength controlled quasi-color-free laser diode (QCFLD) transmitter with either destructively interfered beating or single-sideband filtering after receiving at a remote node, the 100-km long-reach (LR) carrierless millimeter-wave over fiber (MMWoF) link with directly-encoded orthogonal frequency-division multiplexing (OFDM) at 10-15 Gbit/s in optical wired and MMW wireless domains is experimentally demonstrated. The optically heterodyned MMW OFDM data by the destructively interfered beating obtains more gain from the RF amplifier than that without carrierless operation, as the MMW carrier with reduced power no longer dominates the gain competition. The destructively-interfered-beating 16-QAM OFDM data can transmit over 100-km SMF and 10-m free-space. The modulation bandwidth can be enhanced from 2 GHz to 2.5 GHz with a raw data rate of 10 Gbit/s after the OFDM subcarrier sidelobe filtering process. The sidelobe filtering suppresses the impact of the QCFLD chirp on the signal-to-noise of the optically heterodyned beating MMW carrierless OFDM data when reducing the sidelobes of each OFDM subcarrier. Besides, the single-sideband-filtered OFDM data can also obtain a higher gain than the double-sideband one due to the relief of RF amplifier saturation. Even though the noise located at the conjugated data band involves in the frequency-down-converted data after MMW down-mixing, the single-sideband-filtered OFDM data still allows the transmission of 8-QAM single-sideband OFDM data with 2 GHz over 100-km in SMF and 10-m in free-space at a raw data rate of 6 Gbit/s in one single-sideband and 12 Gbit/s at both sidebands. In comparison, the destructively-interfered-beating scheme offers large bandwidth and high spectral usage efficiency of 4 bit/s/Hz, whereas the single-sideband-filtering scheme effectively broadens the available bandwidth by saving another spectral sideband for allocating other carriers and data, which facilitate advantages including doubled band usage and half modulation power consumption. Both schemes offer comparable performance for future long-reach carrierless MMWoF applications.

By remotely heterodyning two independent laser carriers, the long-reach 60-GHz millimeter-wave-over-fiber (MMWoF) link is demonstrated for the Volterra series filtered quadrature amplitude modulation orthogonal frequency division multiplexing (QAM-OFDM) transmission with nonlinear noise suppression, which enables 13-Gbps data delivery through 50-km single-mode fiber (SMF) and 3-m free-space links. A wavelength tunable colorless laser diode transmits the Volterra filter equalized QAM-OFDM data to remotely couple with a localized single-mode laser carrier at the optical receiving end of the MMWoF system. Such an incoherently coupled dual-mode carrier facilitates the optical single-carrier modulation to suppress chromatic dispersion induced power fading effect of the SMF transmitted QAM-OFDM data. The 2nd+3rd-order nonlinear noise induced by direct modulation, heterodyne conversion, and phase fluctuation of the incoherently coupled dual-mode carrier is corrected with the Volterra filter equalization to upgrade the decoded signal-to-noise ratio (SNR) by >2 dB. After remotely heterodyning the downstream and the localized carriers with mutual incoherence in between, the 16-QAM OFDM transmission at a data rate up to 13.2 Gbps is successfully delivered over 3-m wireless link, which reveals the FEC certificated error vector magnitude of 14.1%, SNR of 17 dB, and bit error rate of 1.7 × 10−3.

The TE/TM-mode spectral-separated C-rich SiC ring waveguide is employed to demonstrate polarization-dependent amplitude/polarization shift keying (ASK/PolSK) “AND” logic gate. The plasma-enhanced chemical vapor deposition-grown C-rich SiC film exhibits a nonstoichiometric SiC nano-cluster phase structure with a C/Si atomic ratio of 1.28, which provides an efficient nonlinearity of γ = 4.3 × 102 W−1m−1 and n2 = 2.44 × 10−12 cm2/W to demonstrate the “AND” gating between incoming ASK and PolSK data streams. By carefully designing the polarization preference of the ring waveguide structure, the TE/TM-mode-dependent transmission combs are spectrally separated because of the high birefringence of the waveguide optically triggered by the incoming pulsed stream. This type of a polarization dependent spectral notch can be utilized to perform the polarization-dependent all-optical AND gating, which was done in the current study by inserting a dual-format modulated pump and a continuous-wave probe into a ring waveguide. Output of the probe can be cross-wavelength modulated to provide the exact “AND” gating between the ASK and PolSK streams only when the pump is set to the ON state and the polarization of the pump is parallel to the corresponding notch of the ring waveguide throughput. This type of C-rich SiC ASK/PolSK AND logic gate is fully compatible with silicon-based complementary metal-oxide-semiconductor (CMOS) technology, which also has the advantages of low power consumption and enables polarization engineering for future photonic data logics.

Thermal-dependent transmission performance and long-term stability of a single-transverse-mode (SM) vertical-cavity surface-emitting laser (VCSEL) with directly pre-leveled 16-quadrature amplitude modulation orthogonal frequency-division multiplexing (16-QAM OFDM) data over 100 m OM4 multi-mode-fiber (MMF) are demonstrated. Although narrowing the oxide-confined aperture to 3 μ m enables the SM VCSEL with low threshold current of 0.21 mA and high modulation bandwidth of 21.4 GHz, this technology also enlarges the insulating oxide area to accumulate the heat for raising core temperature. This induces a harsh environment as the core temperature persistently increases without dissipation even under the water-cooling control at 20 °C. As a result, the SM VCSEL can only guarantee a stable operation for 1.5 h under the encoding of QAM-OFDM data for transmission. After optimization, the SM VCSEL successfully supports a back-to-back transmission capacity as high as 96 Gbit/s. With the assistance of OFDM pre-leveling technique, the 96-Gbit/s QAM-OFDM data transmission is qualified over 100 m OM4 MMF with a receiving power penalty as low as 1.3 dB.

Passive mode locking of erbium-doped fiber lasers (EDFLs) started by different two-dimensional (2-D) saturable absorbers (SAs) is demonstrated and compared. The self-amplitude modulation (SAM) coefficients of four 2-D SAs, including graphene, MoS2, and n-/p-type Bi2Te3, are also estimated to compare their mode-locking performance at first stage. By analyzing the nonlinear absorption of those 2-D SAs, graphene possesses the largest SAM coefficient $(\gamma _{{\rm{Graphene}}})$ of 8.7x10–4 better than other 2-D SAs ( $\gamma _{{\rm MoS}2}= 5.5\times 10^{\hbox{--} 4}$ , $\gamma _{{\rm n-Bi2Te}3}= 7.2\times 10^{-4}$ , and $\gamma _{{\rm p-Bi2Te}3}= 7.9\times 10^{\hbox{--} 4}$ ). When operating the EDFL under low-gain condition, the mode-locked EDFL pulsewidth is mainly correlated with the SAM coefficient of SA. All of these 2-D SAs can generate the sub-700 fs EDFL pulsewidth at first mode-locking stage. In particular, graphene can produce the narrowest EDFL pulse with 615-fs pulsewidth because of its largest SAM coefficient to start up the mode locking. When inducing the soliton mode locking by mutually compensating the group-delay dispersion and self-phase modulation, the pulsewidth can be further compressed to sub-400 fs with enlarging pumping power. The graphene mode-locked EDFL effectively compresses its soliton pulsewidth to 343 fs with the widest spectral linewidth of 7.86 nm among all cases. All the obtained EDFL pulses exhibit similar compression ratio of ∼0.55.

A 28-GHz millimeter-wave (MMW) carrier optically heterodyned from an orthogonally polarized tri-color (3λ-⊥-SCM) transmitter, which exhibits single-carrier modulation (SCM) to suppress the dispersion induced fading distortion after long-reach transmission, is demonstrated for building up the long-reach MMW-over-fiber with a distance of 75 km. The SCM-based encoding is obtained by seeding the tri-color master into slave colorless laser diode, which only supports TE-mode feedback with a polarized suppression ratio over 40 dB. After resuming back to the SCM tri-color optical carrier with orthogonal polarization (3λ-⊥-SCM), its delivered data can suppress the intensity noise induced by beating between adjacent modes such that the single-to-noise (SNR) can be improved by 2 dB. Comparing with the traditional parallel polarized multi-carrier modulation (MCM) based tri-color optical carrier (3λ-//-MCM), the orthogonally polarized tri-color optical carrier with SCM (3λ-⊥-SCM) can deliver 64 quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM OFDM) data with its maximal encoding a bandwidth of 8.3 GHz (50 Gbit/s), which provides the error vector magnitude (EVM) of 8.8%, the SNR of 21.2 dB and the bit error rate of 3.5 × 10–3 after passing through a 75-km-long single-mode fiber. To perform the MMW wireless access network (WAN) link after 75-km fiber wired transmission, the heterodyned 28-GHz MMW carrier is obtained from the orthogonally polarized SCM tri-color optical carrier (3λ-⊥-SCM) with its peak power improved by 29 dB (from –50 to –31 dBm) and CNR enhanced by 17 dB (from 32 to 49 dB), as compared to those of the parallel polarized MCM tri-color case (3λ-//-MCM). After wireless transmission for 10-m with horn-antenna pair in free space, the maximal encoding bandwidth of the 16-QAM OFDM delivered by the orthogonally polarized SCM tri-color optical carrier (3λ-⊥-SCM) is 4.5 GHz (with 18 Gbit/s capacity).

Binuclear platinum(II) complexes with strong Pt-Pt interactions are an interesting class of luminescent materials, of which photophysical properties could be controlled via multiple ways through organic ligands and Pt-Pt distance. While a number of binuclear platinum(II) complexes have been developed with tunable emissions, achieving high photoluminescence quantum efficiency (PLQE) remains challenging and of great interest. Here we report the synthesis and characterization of a series of binuclear 2,4-difluorophenylpyridine platinum(II) complexes bridged by thiazol-2-thiolate ligands with different bulkiness. The three complexes were found to have short Pt-Pt distances ranging from 2.916 to 2.945 Å. The strong Pt-Pt interactions lead to pronounced metal-metal-to-ligand charge transfer (MMLCT) absorptions between 450 and 500 nm, and strong

By using a multi-color laser diode carrier with orthogonal polarization and single-carrier modulation, the long-reach single-mode fiber (SMF) passive optical network and millimeter-wave wireless access network (WAN) with carrying narrow-band and channelized discrete multitone (DMT) data format at >1 Gbit/s/channel are demonstrated for 5G wireless mobile applications. For fiber wireline transmission from central office to remote node, the multi-color laser diode is directly encoded by DMT with quadrature amplitude modulation (QAM) levels ranged from 64 to 1024, and the total raw data rate of the received DMT can maintain as high as 88 Gbit/s at a limit modulation bandwidth of 9.125 GHz. The allowable data band consisting of 0.07-6 GHz for 1024 QAM, 6-9 GHz for 512 QAM and 9-9.125 GHz for 256 QAM is achieved even after long-reach transmission in 75-km-long SMF spool. For wireless transmission from remote node to user end with 28-GHz millimeter-wave carrier after optical heterodyne, the wireless transmission distance can lengthen up to 10 meters with allowable data capacity optimized to 29.6 Gbit/s with a modulation bandwidth of 4.1 GHz in total. Consequently, the achievable bit-loaded data band is 256 QAM within 0.07-2.5 GHz and 64 QAM within 2.5-4.1 GHz for 5G mobile WAN transmission via horn antenna pair.

By passing a collimated red/green/blue laser diode (R/G/B-LD) beam through a yellow-orange luminescent Lu3Al5O12:Ce3+/CaAlSiN3:Eu2+ (LuAG:Ce/CASN:Eu) phosphor glass, divergent white light with a color rendering index (CRI) beyond 80 at a correlated color temperature (CCT) of 6500 K is obtained for visible light communication (VLC) beyond 10 Gbps. The CCT of white light is unique as it can be tuned by flexibly adjusting the R/G/B-LD power ratio. Thinning the LuAG:Ce/CASN:Eu phosphor glass to 0.8 mm greatly improves the transmission performance of the white light but inevitably degrades its CRI to 41.1 at a CCT of 6509 K. In contrast, a 1.0 mm thick phosphor effectively enlarges the CRI up to 80.4 at a CCT of 6560 K while reducing the red and blue power. The trade-off between the phosphor glass thickness and R/G/B-LD power is studied to optimize the cold-white-light CRI beyond 80 and the white-light VLC up to 10.4 Gbps.

The C-rich SiC x with enhanced optical nonlinearity is employed to fabricate ring waveguides to perform picosecond optical switching of pulsed data streams under the wavelength conversion scheme. The C-rich SiC x film after 60-minute annealing exhibits abundant graphite-like (sp2 -like) C-C bonds resulting in the increase of its Kerr coefficient. Under transverse electric mode polarized pump-probe analysis, the continuous-wave transmittance comb spectrum of the C-rich SiC x -based ring waveguide shows a higher Q -factor than for transverse magnetic mode analysis. The red-shift of the transmission comb under a peak pumping power of 4.3 W increases from 0.12 to 0.14 nm as the nonlinear refractive index of the C-rich SiC x increases from 1.37 × 10–12 to 2.38 × 10–12 cm2/W through increasing the annealing time from 0 to 60 min. The picosecond optical switching of pulsed bit data in the C-rich SiC x ring waveguide provides an optimized extinction ratio (ER), a signal-to-noise ratio (SNR), and a bit-error rate (BER) of 8.1 dB, 8.2 dB, and 1.7 × 10–11, respectively. After matching the probe wavelength with the red-shifted transmittance comb, the wavelength-converted data shows an inverted format with optimized ER, SNR, and BER of 7.9 dB, 8.1 dB, and 7.8 × 10–10, respectively. The annealing regrown C-rich SiC x can perform better nonlinear optical switching than reported so far for ultrafast data processing in photonic integrated circuits.

By using a 512-quadrature amplitude modulating-orthogonal frequency division multiplexing (512-QAM OFDM) data stream with universal filtered multicarrier (UFMC) process to directly encode a quasi-color-free laser diode (QCFLD) with dual-mode carrier, a long-reach 28-GHz millimeter-wave over fiber (MMWoF) link over 50-km single-mode fiber (SMF) is demonstrated for future fiber network with 5G wireless link. At the fiber-wired optical transmission stage, the dual-mode QCFLD can support raw data rates up to 54, 42, and 24 Gbit/s after 0, 25, and 50-km SMF transmissions. The data-rate degradation results from chromatic dispersion induced power fading effect. The 28-GHz MMW carrier optically heterodyned at remote node with a carrier-to-noise ratio of 53.5 dB is generated after 25-km SMF propagation, which achieves 6-m free-space transmission at 16 Gbit/s. Lengthening the SMF to 50 km still allows the MMWoF for wireless transmission at 16-Gbit/s over 5 m and 14-Gbit/s over 10 m. To favor the 5G wireless access with high data capacity, the UFMC processed QAM-OFDM was further adopted for noise suppression via sidelobe filtering operation. By lengthening the cyclic prefix and the filter window for the OFDM, the tradeoff between data quality and net-data-rate ratio without and with UFMC process is discussed. With UFMC, the MMWoF transmission capacity can deliver 3-GHz wide 32-QAM UFMC processed OFDM data at 15 Gbit/s over 50 km in SMF and 10 m in free space. Even within a limited subcarrier bandwidth as narrow as 140 MHz for practical 5G users, the 512-QAM UFMC data can be allocated to provide a raw data rate of 1.26 Gbit/s.

A quasi-color-free laser diode (QCFLD)-based 60-Gbit/s long-reach (LR) OFDM-PON with dispersion management is demonstrated. After injection locking, the QCFLD achieves an ultimate back-to-back transmission capacity of 60 Gbit/s. After propagating through 25-, 50-, and 75-km single-mode fiber (SMF)-based LR-OFDM-PON, the RF power fading effect induces signal deterioration to inevitably degrade the transmission capacities of the QCFLD at 45, 27, and 21 Gbit/s, respectively. To avoid the RF fading effect, dispersion management is introduced by using different segments of nonzero dispersion-shifted fiber (NZ-DSF) and dispersion compensating fiber (DCF) with corresponding dispersion constants of +5.6 and −5 ps/nm/km, respectively. Using either 25-km NZ-DSF or 25-km DCF enables the OFDM-PON to operate at up to 57 Gbit/s. Combining the 25-km NZ-DSF with the 25-km DCF establishes the near-zero dispersion to effectively support the 50-km LR OFDM-PON up to 51 Gbit/s, which is nearly twice data rate as compared to the 50-km SMF case. For implementing the 75-km LR OFDM-PON, the scenario of 25-km NZ-DSF in connection with 50-km DCF is employed to achieve 48-Gbit/s transmission capacity. In comparison with the same OFDM-PON constructed with 75-km SMF, the achievable data rate is doubled through the synergy of the LR OFDM-PON technology with dispersion management.

A nonstoichiometric Si1− x Ge x with composition ratio dependent saturable absorption prepared by vaporized synthesis and chemical exfoliation is performed to passively mode-lock the Erbium-doped fiber laser (EDFL). The Si1− x Ge x with varied Ge/Si composition ratio from 3 to 16 exhibits tunable nonlinear modulation depth from 17% to 22%, where the Si1− x Ge x with the highest Ge content performs the largest nonlinear modulation depth. When operating the EDFL in the self-amplitude modulation region, the Si1− x Ge x with Ge/Si composition ratios of 3, 9, and 16 self-starts the EDFL pulsation with pulsewidths of 820, 760, and 730 fs. When operating the EDFL in high gain region, the self-phase modulation induced soliton compression dominates the repulsation of passively mode-locked EDFL, which slightly shrinks the EDFL pulsewidth from 346 to 338 fs. All these demonstrations are premier and important to explore the superior nonstoichiometric Si 1− x Ge x saturable absorbers for ultrafast fiber lasers.

By using the Lu 3 Al 5 O 12 :Ce 3+ /CaAlSiN 3 :Eu 2+ phosphor codoped fluorescent glass as a phosphor in front of an InGaN laser diode (LD), a novel white-lighting and visible light communication (VLC) module is demonstrated. By enlarging the fluorescent glass thickness from 0.7 to 1 mm, the CCT of the generated white light is increased from 7373 to 25000 K, and the maximal illuminance is enlarged from 1306 to 1356 lux. The pure LD-beam-based VLC can lengthen its transmission distance from 0.5 to 16 m, associated with allowable data rate slightly decreased from 14.8 to 10.8 Gb/s. When using the divergent white light as a carrier for VLC transmission, the allowable data rate upgrades from 1.6 to 4.4 Gb/s within 0.5-m distance in free space by thinning the fluorescent glass from 1 to 0.7 mm. Lengthening the white-lighting distance to 1 m for the VLC system still permits 16-QAM OFDM data transmission as high as 2.8 Gb/s. Such a Lu 3 Al 5 O 12 :Ce 3+ /CaAlSiN 3 :Eu 2+ phosphor codoped fluorescent glass not only converts the blue LD beam for white lighting efficiently, but also preserves sufficient data capacity with acceptable signal-to-noise ratio for indoor VLC application.

A GaN blue laser diode (BLD)-based visible-light communication link is demonstrated in a seawater environment to provide 16-quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM OFDM) data transmission at 14.8 Gbps over 1.7 m. Lengthening the seawater distance to 10.2 m only decreases the transmission data rate by 4 Gbps, as caused by the frquency response limitation of the used avalanche photodiode. To optimize the QAM-OFDM transmission, the sampling rate of the encoded data is compromised to avoid the aliasing and oversampling effects during the waveform extraction procedure. The sampling rate is optimized to 3–5 times of the encoded data bandwidth for suppressing peak-to-average power ratio. Oversampling not only filters out background noise but also attenuates data amplitude to degrade transmission performance. Without using the multicarrier spectrally filtered OFDM, the 16-QAM OFDM data format only promotes the transmission capacity of BLD up to 7.6 Gbps in seawater. With spectrally filtering out the sidelobes of each OFDM subcarrier, the allowable modulation bandwidth is greatly improved from 1.9 to 2.7 GHz, as the intercarrier interference induced crosstalk between subbands is relieved to improve the SNR of the carried data with a raw data rate of up to 10.8 Gbps.

The SiGeC waveguide based ultrafast all-optical switching by using the cross-absorption modulation (XAM) effect is demonstrated to perform the wavelength conversion and format inversion of a pulsed return-to-zero on–off keying (PRZ-OOK) data stream. Under the intensively optical data-bit illumination as the pump, the two-photon absorption (TPA) effect is observed to induce free carriers in the SiGeC for absorbing the power of the probe beam. This free-carrier absorption (FCA) procedure inversely modulates the probe beam to cause the XAM switching via the intensively pumping data-bit-induced TPA/FCA process. With employing the Ge content into the SiC matrix, the picosecond free-carrier lifetime of the SiGeC can be obtained by further degrading the injected pumping energy under all-optical switching operation. With reducing the pumping energy from 0.5 nJ to 22 pJ, the effective response time of the all-optical XAM switching successfully shortens from 120 to 2 ps. Experiments declare that even a relatively l...

Single-channel 50-Gbit/s 4-level pulse amplitude modulation (PAM-4) and 62-Gbit/s orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) direct encoding of an uncooled coarse wavelength division multiplexer (CWDM) 100-Gbit/s distributed feedback laser diodes (DFBLD) transmitter module at 1310-nm transmitter interdata center transmission over 10-km single-mode fiber (SMF) are demonstrated. To enable preleveled 16-QAM OFDM and PAM-4 data transmissions at 62 and 50 Gbit/s, the 1310-nm channel of the DFBLD CWDM transmitter provides modulation bandwidth of 15 GHz, side-mode suppression ratio of 48 dB, and relative intensity noise of −126 dBc/Hz. For encoding the PAM-4 data, the 1310-nm channel of the CWDM DFBLD 100-Gbit/s transmitter achieves transmission capacities of 58 and 50 Gbit/s after BtB and 10-km SMF transmissions, respectively. Instead of supporting the back-to-back 16-QAM OFDM with the transmission at 62 Gbit/s with forward error correction (FEC) certified BER of 3.3 × 10−3, such a CWDM 100-Gbit/s DFBLD transmitter module can still maintain its highest data rate capacity to indicate a receiving power penalty of 0.35 dB even after 10-km SMF propagation. This is mainly attributed to the selected channel wavelength of the narrow-linewidth DFBLD, which suffers from extremely low chromatic dispersion and RF fading effect.

Using the evanescent-wave saturation effect of hydrogen-free low-temperature synthesized few-layer graphene covered on the cladding region of a side-polished single-mode fiber, a blue pump/infrared probe-based all-optical switch is demonstrated with specific wavelength-dependent probe modulation efficiency. Under the illumination of a blue laser diode at 405 nm, the few-layer graphene exhibits cross-gain modulation at different wavelengths covering the C- and L-bands. At a probe power of 0.5 mW, the L-band switching throughput power variant of 16 μW results in a probe modulation depth of 3.2%. Blue shifting the probe wavelength from 1580 to 1520 nm further enlarges the switching throughput power variant to 24 mW and enhances the probe modulation depth to 5%. Enlarging the probe power from 0.5 to 1 mW further enlarges the switching throughput power variant from 25 to 58 μW to promote its probe modulation depth of up to 5.8% at 1520 nm. In contrast, the probe modulation depth degrades from 5.1% to 1.2% as the pumping power reduces from 85 to 24 mW, which is attributed to the saturable absorption of the few-layer graphene-based evanescent-wave absorber. The modulation depth at wavelength of 1550 nm under a probe power of 1 mW increases from 1.2% to 5.1%, as more carriers can be excited when increasing the blue laser power from 24 to 85 mW, whereas it decreases from 5.1% to 3.3% by increasing the input probe power from 1 to 2 mW to show an easier saturated condition at longer wavelength.

Long-reach fiber-wireless access link using a dual-mode vertical-cavity surface-emitting laser (DM-VCSEL) is established for carrierless millimeter-wave (MMW) transmission with suppressed RF fading. By destructively interfered beating the orthogonally polarized dual carrier from the DM-VCSEL, the remotely beat MMW central carrier suppresses its central peak power up to 33 dB, which ensure more gain for the carried quadrature-amplitude modulation orthogonal frequency-division multiplexing (QAM-OFDM) data during electrical amplification to lengthen the distance of wireless link. With suppressing the MMW central carrier and mitigating the RF fading by destructively interfered beating and optical single-carrier modulation of the DM-VCSEL, the received optical signal-to-noise ratio as high as 18.1 dB is determined after fiber transmission. Such a long-reach 38-GHz carrierless MMW over fiber system enables 12-Gb/s 16-QAM OFDM data transmission over 50 km in single-mode fiber and 4 m in free space. After the proposed fiber-wireless access, the single-carrier modulated QAM-OFDM data certifies to pass the forward error correction criterion with an error vector magnitude of 17.2% and a bit error rate of 3.6 × 10–3.

By delivering a reference carrier through adjacent dense-wavelength-division-multiplexing (DWDM) channel to remotely beat with the downstream transmitted optical carrier, a full-duplex millimeter-wave DWDM passive-optical-network (MMW-DWDM-PON) is demonstrated to transmit 36- ${\text{Gb/s}}$ data over 25-km single-mode fiber (SMF) and to remotely deliver a 28-GHz MMW carrier for wireless 6- ${\text{Gb/s}}$ data transmission. Such a remotely recombined dual-mode beating scheme provides baseband 36- ${\text{Gb/s}}$ data with corresponding bit error rate (BER) of 2.7 × 10 −3, which is better than the directly dual-mode injection-locked colorless Fabry-Perot laser diode (FPLD) does because of the less fiber chromatic dispersion during 25-km SMF transmission. In a hybrid 25-km SMF-wired and 1.6-m wireless link, it successfully transmits 4- ${\text{Gb/s}}$ data to fit the forward error correcting criterion. By maintaining the free-space distance at 1.6 m, the allowable raw data rate for MMW wireless transmission can be increased up to 6 ${\text{Gb/s}}$ with BER of 1.9×10−3. For optical baseband upstream transmission, the 36- ${\text{Gb/s}}$ data is also directly encoded onto the upstream colorless FPLD injection-locked by reusing the downstream pure carrier delivered through adjacent DWDM channel, and the received data reveals a BER of 2.9 × 10 −3.

By changing the transverse-mode spectral linewidth of vertical cavity surface emitting lasers (VCSELs) at 850 nm, the directly encoded four-level pulse amplitude modulation data transmission performance over 100-m-long OM4 multimode fiber (MMF) are demonstrated and compared. The multi-mode VCSEL chip with the largest aperture of $11~\mu \text{m}$ reveals the widest spectral linewidth and the highest optical power, but provides the smallest modulation bandwidth to support only 44- and 28-Gb/s data rates for back-to-back (BtB) and 100-m OM4 MMF transmission cases, respectively. By shrinking the aperture size to reduce transverse-mode number, the few-mode VCSEL with the strongest throughput power enables a BtB transmission capacity as high as 52 Gb/s. However, its modal dispersion induced after OM4 MMF transmission inevitably degrade the data rate to 32 Gb/s. In contrast, the single-mode VCSEL with the smallest aperture of $3~\mu \text{m}$ reveals the highest modulation bandwidth and negligible modal dispersion to show competitive BtB transmission capacity with that of the few-mode VCSEL. In particular, the single-mode VCSEL successfully achieves a data rate of 34 Gb/s with a power penalty as low as 1.4 dB, after 100-m OM4 MMF transmission.

Violet laser diode (VLD) based white-light source with high color rendering index (CRI) for lighting communication is implemented by covering with Y3Al5O12:Ce3+ (YAG:Ce) or Lu3Al5O12:Ce3+/CaAlSiN3:Eu2+ (LuAG:Ce/CASN:Eu) phosphorous diffuser plates. After passing the beam of VLD biased at 70 mA (~2I th ) through the YAG:Ce phosphorous diffuser, a daylight with a correlated color temperature (CCT) of 5068 K and a CRI of 65 is acquired to provide a forward error correction (FEC) certified data rate of 4.4 Gbit/s. By using the VLD biased at 122 mA (~3.5I th ) to excite the LuAG:Ce/CASN:Eu phosphorous diffuser with 0.85-mm thickness, a warm white-light source with a CCT of 2700 K and a CRI of 87.9 is obtained at a cost of decreasing transmission capacity to 2.4 Gbit/s. Thinning the phosphor thickness to 0.75 mm effectively reduces the required bias current by 32 mA to achieve the same CCT for the delivered white light, which offers an enlarged CRI of 89.1 and an increased data rate of 4.4 Gbit/s. Further enlarging the bias current to 105 mA remains the white-light transmission capacity at 4.4 Gbit/s but reveals an increased CCT of 3023 K and an upgraded CRI of 91.5.