PAM-4 Data Transmission Research Articles

Evaluating PAM-4 Data Transmission Quality Using Multi-Dimensional Mapping of Received Symbols

Evaluating PAM-4 Data Transmission Quality Using Multi-Dimensional Mapping of Received Symbols

Local oscillators-free chip-enabled W-band wireless IM-DD PAM-4 data transmission with simultaneous dual-laser modulation and envelope detection.

Wireless data traffic is expected to exponentially increase in the future, and meeting this demand will require high data rate photonic-wireless links operating in the W-band (75-110 GHz). For this purpose, pulse-amplitude-modulation with four levels (PAM-4)-based intensity modulation and direct detection (IM-DD) photonic-wireless systems are preferred due to their simplified configuration. In this Letter, we present an experimental demonstration of an IM-DD PAM-4 photonic-wireless link in the W-band, leveraging a monolithic dual-laser photonic chip to enhance integration. Through injection-locking by an optical comb, the chip generates a W-band wireless signal via photo-mixing with a photodiode. This comb injection approach facilitates the phase correlation of the chip's two modes, resulting in a stabilized beat note. Additionally, the on-chip integration of the dual lasers enables the modulation of the two modes with a single modulator, improving the signal-to-noise ratio (SNR) while eliminating the need for extra splitters or combiners. Meanwhile, the envelope detector (ED) plays a crucial role in the simplified configuration, contributing to the overall decrease in size, weight, power, and complexity of the system. The integration of the chip-based phase-locked light source and the utilization of the ED thus signify noteworthy features of our experimental setup, which functions without the necessity of both optical and electrical local oscillators. PAM-4 signal modulation is simultaneously applied to the two coherent optical carriers. Our experiments have effectively transmitted 5 and 10 Gbaud PAM-4 W-band wireless signals in a cost-effective, lightweight, and straightforward configuration, achieving a line data rate of up to 20 Gbit/s economically. These experimental results demonstrate the practical potential of implementing fully integrated photonic-wireless transmitters.

50 Gbit/s PAM4 Data Transmission Over 500-m Single-Mode Fiber Using an 880-nm Single Mode VCSEL

Error-free 50 Gbit/s PAM4 data transmission over 500-m single mode fiber was successfully realized using our oxide-confined 880-nm single-mode high-speed VCSELs. This transmission was accomplished because of the flat frequency response of the VCSEL across a wide bias span. Static characteristics and high-speed modulation properties at room temperature and high operation temperature were studied in detail. Data transmission experiments for the 880-nm VCSEL with 4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> oxide-aperture diameter was performed. A 50-Gbps PAM4 module was packaged for data transmission. Error-free 50 Gbit/s PAM4 data transmission over 500-m single mode fiber was successfully realized. The proposed VCSEL is fit for the 400G DR8 module because of its 500-m single-channel 50 Gbit/s error-free transmission. Compared with commonly used DML, VCSELs are evidently advantageous in cost and power consumption.

Error-free PAM-4 transmission by a high-speed plastic optical fiber without forward error correction.

This Letter reports, to the best of our knowledge, the first study in which error-free four-level pulse-amplitude modulation (PAM-4) transmission has been achieved using a graded-index plastic optical fiber (GI POF) without the use of forward error correction (FEC) techniques, at a high data rate (>50Gb/s), for short-reach applications (10 m). The GI POF that is developed has the characteristic microscopic heterogeneities in the fiber core material, which provide distinct mode coupling and significantly stabilize PAM-4 data transmission. The results of the study in this Letter indicate that the GI POF achieves highly stable PAM-4 transmission without the need for the current FEC techniques, which seriously increase the communication delay and power consumption of the transmission systems. Our GI POF material is paving the way for "material changes the system" approaches for achieving unprecedented optical interconnects in real time at a high speed and with low power consumption.

Low-chirp push-pull dual-ring modulator with 144 Gb/s PAM-4 data transmission.

We experimentally demonstrate a low-chirp high-speed push-pull dual-ring modulator. The device is formed by two parallel cascaded add-drop ring modulators which has a Fabry-Perot resonance spectrally similar as electromagnetically induced transparency (EIT) effect. Differential drive signals are applied to the two rings to shift the individual resonances towards opposite directions, creating intensity modulation with suppressed frequency chirp. We present static and dynamic characterization of the device, including chirp parameter. We also demonstrate 144 Gb/s PAM-4 data transmission with 1-km standard single-mode fiber (SSMF) with BER below hard-decision forward error correction (HD-FEC) threshold with 7% overhead.

Passively mode-locked quantum dash laser with an aggregate 5.376 Tbit/s PAM-4 transmission capacity.

This paper presents an InAs/InP quantum dash (QD) C-band passively mode-locked laser (MLL) with a channel spacing of 34.224 GHz. By using this QD-MLL we demonstrate an aggregate 5.376 Tbit/s PAM-4 data transmission capacity both for back-to-back (B2B) and over 25-km of standard single mode fiber (SSMF). This represents the first demonstration of QD-MLL acting as error-free operation at an aggregate data transmission capacity of 5.376 Tbit/s for some filtered individual channels. This finding highlights the viability for InAs/InP QD lasers to be used as a low-cost optical source for data center networks.

100-Gbit/s/λ EML Transmitter and PIN-PD+TIA Receiver-Based Inter-Data Center Link

Beyond 100-Gbit/s/λ high-speed inter-data-center link composed by hybridly integrated electro-absorption modulator (EAM) and distributed feedback laser diodes (DFBLD)-based transmitter at 1306 nm, and received by a PIN-PD + TIA optical receiver is demonstrated to carry 104-Gbit/s pre-emphasized PAM-4 data for 2–10 km single mode fiber (SMF) propagation. The EAM + DFBLD transmitter offers an average power of −1.5 dBm, an excellent side mode suppression ratio of 53 dB, an on/off extinction ratio up to 10 dB, an analog bandwidth of 25 GHz, and a relative intensity noise of -137 dBc/Hz. The PIN-PD + TIA module exhibits 30-GHz receiving bandwidth. For on-off keying (OOK) format, the allowable data rates at 62 and 60/54 Gbit/s for BtB and 2-km/10-km SMF cases obtain receiving BER of 1.48 × 10−13 and 3.4 × 10−14/1.77 × 10−14 qualified for error-free telecommunication. Even at simulated inter-data center link, the receiving power sensitivity and power penalty at 54 Gbit/s can achieve −6.43/−6.26 dBm and 0.07/0.24 dB after 2-/10-km SMF propagation. To efficiently utilize the limited transmitter bandwidth, the directly encoded PAM-4 data transmission reveals qualified BER slightly enlarged from 1.4 × 10−4 to 2.3 × 10−4 when transferred from back-to-back to 2-km SMF transmission. Lengthening the distance to 10-km SMF degrades the maximal PAM-4 data rate to 50 GBaud with a received BER of 2.3 × 10−4 (less than KP4-FEC criterion). The 50 GBaud PAM-4 link provides receiving power penalty of 0.11/0.24 dB after 2-/10-km SMF propagation, which is attributed to the narrow-linewidth DFBLD responsible for extremely low RF fading effect under nearly zero dispersion condition. The transmitting frontend with amplitude/phase pre-emphasis function makes the receiving end compact and cost-effective, which exhibits the higher spectral usage efficiency of 4 bit/s/Hz and the better receiving sensitivity of −5.5 dBm at the lower power budget of 2.8 fJoule/bit than previous works.

Inverse-Design and Demonstration of Ultracompact Silicon Meta-Structure Mode Exchange Device

Data exchange among different mode channels is indispensable for optical communication system adopting mode-division multiplexing. Traditional mode exchange device is complex in procedure and large in footprint, which makes it not suitable for dense and large-scale photonic integration. Utilizing the degree of freedom of silicon meta-structure, we design an ultracompact and optically broadband mode exchange device between TE0 and TE1 modes by the step-by-step inverse-design method considering the axisymmetric constraint. Simulation result shows that it is robust to a temperature variation of 100 K and a fabrication error of ±20 nm. The fabricated device is 4 × 1.6 μm2 in footprint. The simulated conversion efficiencies are over 73% and 71% for TE0 to TE1 and TE1 to TE0 within the whole C-band, and the experimental results are about 10% lower than the simulation. 40 Gbps OOK and 25 GBaud PAM-4 data transmission through the device are carried out, which shows good signal quality. We envision that the device...

42.8 Gbit/s PAM-4 data transmission over low-loss electrical backplane

Demonstrated is a record serial transmission rate of 42.8 Gbit/s by sending four-level pulse amplitude modulated (PAM-4) data over a low-loss Megtron 6 electrical backplane. The data is processed and equalised using early late gate timing recovery and a finite-impulse-response-based least-mean-squares equaliser. Bit error rate performance is reported over several different links.