Reduction of mode partition noise of FP-LD by using Mach-Zehnder interferometer for RSOA-based DWDM applications.

We investigate reduction of mode partition noise of a spectrally sliced Fabry-Perot laser diode (FP-LD) for application to seeded DWDM systems. The proposed scheme for the noise reduction incorporates a fiber-based Mach-Zehnder interferometer (MZI) and a reflective semiconductor optical amplifier (RSOA). The MZI enables to reduce a relative intensity noise (RIN) more than 3 dB with better noise distributions. Experimental results of 10-Gb/s signal transmission exhibit a considerable bit-error-rate (BER) reduction by three orders of magnitude at the given received power. After the noise reduction, the FP-LD is applied to a 10-Gb/s DWDM system as a seed-light-source. In a local-seeding scheme, return-to-zero (RZ) and carrier-suppressed (CS)-RZ signal formats are compared as a function of transmission distance. Furthermore, a back-reflection induced impairment is evaluated in a remote-seeding scheme. We also count the number of useable channels to show the feasibility of DWDM transmission.

800 Gb/s (80 × 10 Gb/s) capacity WDM-PON based on ASE injection seeding.

We demonstrate and characterize 800 Gb/s capacity WDM-PON with an ASE injection seeding. Required total seed power at central office to feeder fiber is 16 dBm for 20 km upstream transmission of 80 channels. We investigate the maximum transmission length according to channels. The transmission length is limited to 39.7 km by intra-channel crosstalk induced by Rayleigh back-scattering, provided that the dispersion is compensated. Also, we investigate the allowable differential path length to evaluate the flexibility of the system.

Pulsed-ASE-seeded DWDM optical system with interferometric noise suppression.

We propose and demonstrate a 10-Gb/s dense wavelength-division-multiplexing (DWDM) optical system based on a pulsed-seed-light source employing a fiber-based Mach-Zehnder interferometer (F-MZI) as an intensity noise suppressor. The transmission results show that the required injection power into a reflective modulator was as low as -18 dBm. The F-MZI can accommodate the polarized seed-light with superior noise characteristics so that the supported DWDM systems double using a single conventional unpolarized seed-light. In addition, an allowable length of the drop fiber is investigated to show the system flexibility.

Noise-suppressed mutually injected Fabry-Perot laser diodes for 10-Gb/s broadcast signal transmission in WDM passive optical networks.

We propose and demonstrate 10-Gb/s broadcast signal transmission in a wavelength-division-multiplexing passive optical network (WDM-PON) by employing a modular-type mutually injected Fabry-Perot laser diodes (MI F-P LDs) as a cost-effective multi-wavelength light source (MWS). We introduce a simple interferometric noise suppression technique with proper electrical filtering to improve transmission performance. The noise suppression doubles the number of supported subscribers with a single MI F-P LDs.

DWDM-PON at 25 GHz channel spacing based on ASE injection seeding.

We demonstrate a 25 GHz-channel-spaced DWDM-PON based on ASE injection seeding. A 60 km transmission at 1.25 Gb/s per channel is available with a 2nd generation FEC. The major limiting factor is the optical back reflection induced penalty. Thus a high gain reflective modulator and/or relocation of the seed light increase the transmission length. We demonstrated 90 km transmission with relocated seed light to remote node.

Low noise GHz passive harmonic mode-locking of soliton fiber laser using evanescent wave interaction with carbon nanotubes.

Passive harmonic mode-locking in soliton fiber laser is presented with excellent noise characteristics by employing a single-walled carbon nanotubes saturable absorber designed to interact with evanescent wave of the laser field. The 34(th) harmonic mode-locking pulses at 943.16 MHz repetition rate were stably generated with 18 mW output power, >50 dB side-mode suppression and -140 dB/Hz relative intensity noise. Soliton energy control with polarization controller further increased the harmonic order to 61st, 1.692 GHz, but with compromised performance. Scaling to higher-order harmonic mode-locking is discussed for practical application in optical communication system.

Long-term Outcomes of Laparoscopic Surgery for Colorectal Cancer.

PURPOSE: The long-term results of a laparoscopic resection for colorectal cancer have been reported in several studies, but reports on the results of laparoscopic surgery for rectal cancer are limited. We investigated the long-term outcomes, including the five-year overall survival, disease-free survival and recurrence rate, after a laparoscopic resection for colorectal cancer. METHODS: Using prospectively collected data on 303 patients with colorectal cancer who underwent a laparoscopic resection between January 2001, and December 2003, we analyzed sex, age, stage, complications, hospital stay, mean operation time and blood loss. The overall survival rate, disease-free survival rate and recurrence rate were investigated for 271 patients who could be followed for more than three years. RESULTS: Tumor-node-metastasis (TNM) stage I cancer was present in 55 patients (18.1%), stage II in 116 patients (38.3%), stage III in 110 patients (36.3%), and stage IV in 22 patients (7.3%). The mean operative time was 200 minutes (range, 100 to 535 minutes), and the mean blood loss was 97 mL (range, 20 to 1,200 mL). The mean hospital stay was 11 days and the mean follow-up period was 54 months. The mean numbers of resected lymph nodes were 26 and 21 in the colon and the rectum, respectively, and the mean distal margins were 10 and 3 cm. The overall morbidity rate was 26.1%. The local recurrence rates were 2.2% and 4.4% in the colon and the rectum, respectively, and the distant recurrence rates were 7.8% and 22.5%. The five-year overall survival rates were 86.1% in the colon (stage I, 100%; stage II, 97.6%; stage III, 77.5%; stage IV, 16.7%) and 68.8% in the rectum (stage I, 90.2%; stage II, 84.0%; stage III, 57.6; stage IV, 13.3%). The five-year disease-free survival rates were 89.8% in the colon (stage I, 100%; stage II, 97.7%; stage III, 74.2%) and 74.5% in the rectum (stage I, 90.0%; stage II, 83.9%; stage III, 59.2%). CONCLUSION: Laparoscopic surgery for colorectal cancer is a good alternative method to open surgery with tolerable oncologic long-term results.