Mitigation of optical multipath interference impact for directly detected PAMn system.

This paper investigates solutions for mitigating multipath interference (MPI) impact for intensity modulation direct detection systems, particularly for PAM4 systems. We propose a scheme that uses a high pass filter (HPF) at the receiver to remove the MPI induced carrier-carrier beat noise and therefore improve the MPI tolerance. The scheme has been verified via theoretical analysis, numerical simulation, and experiment. For a typical optical transmitter based on Mach-Zehnder modulator (MZM) without frequency chirp, over 5dB MPI tolerance can be improved for 106.4Gb/s PAM4 by using the proposed scheme. Investigation was also extended to electro-absorption modulated laser (EML) and directly modulated laser (DML) based optical transmitters. Results show that transient chirping in EML reduces the effectiveness of proposed MPI mitigation scheme. For EML with chirp factor smaller than 1.5, MPI tolerance gain of 2dB is still achievable. However, the scheme is ineffective for typical DML where the adiabatic chirp significantly broadened the laser linewidth.

200G self-homodyne detection with 64QAM by endless optical polarization demultiplexing.

This paper investigates the self-homodyne detection system with orthogonal polarization between pilot and signal (oSHD) through optical polarization demultiplexing of carrier and signal at receiver. Compared to digital demultiplexing, optical demultiplexing provides around a 0.9dB benefit in receiver sensitivity. The impact of crosstalk due to optical demultiplexing has been investigated in terms of carrier-to-signal power ratio, and delay between signal and carrier. Results show that the oSHD system is very tolerant to crosstalk, with a negligible penalty for crosstalk up to -22dB. Experiments were carried out to evaluate the system performance, including polarization tracking performance, long term stability, bit error rate performance, and tolerance to laser linewidth and delay between signal and pilot. 41Gbaud 64QAM oSHD with 200Gb/s net data rate has been realized by using the scheme with receiver sensitivity better than -4dBm, providing a promising candidate solution for 800Gb/s Ethernet.

Innovative magnetic rings for circumferential mucosectomy: preliminary research.

PURPOSE: To improve the procedures used to treat prolapse and hemorrhoids, novel magnetic rings were invented to use in circumferential mucosectomies to avoid the disadvantages of stapling techniques. METHODS: Thirty adult pigs were randomly divided into three groups: Group A (n = 10), which underwent circumferential mucosectomy with novel magnetic rings; Group B (n = 10), which underwent circumferential mucosectomy with conventional magnetic rings and Group C (n = 10), which underwent circumferential mucosectomy with a stapling technique. RESULTS: All pigs underwent the operation successfully, and the mean length of the procedure was similar among the three groups (p > 0.05). There was no bleeding in Group A or Group B, while there was a mean blood loss of 78.32 ± 26.03 ml in Group C (p < 0.01). Three cases of anastomotic stenosis were found in Group C (3/10); two cases were found in Group B (2/10) and no anastomotic stenosis was found in Group A (0/10). The difference between groups A and C was statistically significant (p < 0.05). The cost for the magnetic rings in groups A and B was noticeably lower than that of the stapling techniques in Group C (20.12 ± 3.35 vs. 15.76 ± 2.92 vs. 550.16 ± 29.71 US dollars, p < 0.001). The magnetic rings in groups A and B were spontaneously discharged from the body with the necrotic tissues within 1-2 weeks (8.20 ± 2.73 vs. 9.31 ± 3.62 days, p > 0.05), avoiding the permanent implantation of staples in Group C. The anastomosis site in Group A showed a smoother and more rapid healing process than that in Group B or C. CONCLUSIONS: The innovative magnetic rings we developed for circumferential mucosectomies provide a simple and novel surgical procedure for prolapse and hemorrhoids.

Photonic microwave phase shifter/modulator based on a nonlinear optical loop mirror incorporating a Mach-Zehnder interferometer.

We realize a novel photonic microwave phase shifter/modulator based on a nonlinear optical loop mirror incorporating a Mach-Zehnder interferometer. A near-linear phase shifter exceeding 180 degrees and a phase modulation with 2.5 Gbit/s baseband signal are obtained for a 10 GHz microwave signal by this proposed device.

New transmitter configuration for subcarrier multiplexed DPSK systems and its applications to chromatic dispersion monitoring.

We present a new transmitter configuration using a single dual-electrode Mach-Zehnder Modulator (DE-MZM) for generating DPSK signal and subcarrier simultaneously. We then apply this new configuration to monitoring chromatic dispersion (CD) in DPSK systems by detecting the RF power at both of the clock and subcarrier frequencies. Our investigations show that the method can greatly improve CD monitoring capability. The impact of subcarrier on the DPSK performance is also investigated. Results show that by simply selecting the subcarrier close to half of the DPSK data rate frequency, we can significantly suppress the subcarrier induced power penalty to DPSK signal.

High-speed WDM-PON using CW injection-locked Fabry-Pérot laser diodes.

We propose a new WDM-PON architecture using Fabry-Pérot laser diodes (FP-LDs) that are injection-locked by continuous wave (CW) seed light. The modulation characteristics of the CW light injection-locked FP-LD are first investigated. Both uplink and downlink transmissions at 10 Gb/s are experimentally demonstrated using the proposed CW injection-locked FP-LDs. It is shown that up to 16 laser cavity modes can be selectively injection-locked with side mode suppression ratio larger than 30dB. The effects of the location of FP-LD cavity modes, transmission distance, and injection wavelength detuning on the overall transmission performance are investigated. The possibility of eliminating polarization dependence of the proposed CW injection scheme is also experimentally demonstrated by properly configuring a depolarizer. The deployment cost for the proposed WDM PON is potentially low from the fact that the CW laser sources located at the central office can be shared by many WDM-PONs and low-cost FP-LDs are used as light sources for data rates as high as 10 Gb/s.