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We report the first experimental breakthrough of a net gain of optical signals in a broadband chromium-doped fiber amplifier (CDFA) for next-generation optical communication systems. Current fiber amplifiers, including commercial erbium-doped fiber amplifier, cover only a relatively small portion of the entire transmission bandwidths (1300-1600 nm) of the low-loss windows of silica fibers. The newly developed CDFAs have opened up the possibility of utilizing the 300-nm entire spectrum of the low-loss fibers to further increase the transmission capacity. In this paper, we present the experimental demonstration of a net gain of 1.2 dB employing gain enhancement technique. With the help of an optical-fiber system examination for the CDFA, a 40-Gb/s error-floor free data transmission was successfully demonstrated by realizing the high-speed transmission of signal with gain through the chromium-doped fibers (CDFs). Further gain improvement in the CDFAs employing few-mode or single-mode CDFs will be presented and discussed. [ABSTRACT FROM PUBLISHER]

In order to realize a future 100-Gb Ethernet (100 GbE) transport, 100-Gb/s transmission without 100-GHz-class electronics and optical time-division-multiplexing technique was demonstrated. By using a differential quadrature phase-shift-keying (DQPSK) modulation format and commercially available electronics, 2- and 50-km transmissions of 100-Gb/s signal were successfully achieved over a standard single mode fiber. The receiver sensitivity, chromatic dispersion, and differential group delay tolerances of 100-Gb/s DQPSK signal were also evaluated. Through these evaluations, the possibility of DQPSK modulation for future 100-GbE transport is verified [ABSTRACT FROM PUBLISHER]

We develop an in-service dispersion monitoring technique based on the optical frequency modulation (FM) method and examine its applicability to wavelength division multiplexing (WDM) long-haul transmission systems. This method is insensitive to the group-delay drift induced by environmental perturbations and can measure the dispersion value with its sign (normal or anomalous) accurately only from the received signal light. These features are very attractive for the application in ultralong-haul transmission systems. We implement the in-service dispersion monitor in a 32 × 10.7 Gbit/s WDM transmission system. Accurate dispersion monitoring at a transmission distance of 5950 km is achieved without any bit error rate (BER) penalty. Also, we discuss the applicability of the optical FM method to higher bit-rate systems from the experimental result. [ABSTRACT FROM PUBLISHER]

70-GHz-spaced 40×42.7 Gb/s prefiltered carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) signals have been transmitted over transpacific distances for the first time, using all-Raman repeaters with two pump-wavelengths, dispersion-managed fiber commercially available in volume, and an ETDM receiver. In this paper, first, in order to enhance the spectral efficiency, the impact of bandlimitation to a CSRZ-DPSK signal was experimentally investigated in comparison to a conventional CSRZ-on-off-keying (OOK) signal, and we found that the bandlimitation tolerance of CSRZ-DPSK signal was smaller than that of CSRZ-OOK signal in back-to-back condition. We also confirmed that the prefiltering CSRZ-DPSK signal with up to 65 GHz bandlimitation potentially had better transmission performance than the prefiltered CSRZ-OOK signal. In addition, we found that, although the nonlinear transmission penalty was increased by bandlimitation, this penalty for CSRZ-DPSK signal was smaller than that for CSRZ-OOK signal. Through this study, long-term stability of the transmission performance was also evaluated with low-speed signal polarization scrambling without using any polarization mode dispersion (PMD) compensation. [ABSTRACT FROM PUBLISHER]

We have studied the effect of the dispersion map for the long-haul return-to-zero differential phase-shift-keying system theoretically. The results showed that the self-phase-modulation effect impacted the performance, and it could be possible to reduce its impact by an appropriate map design. [ABSTRACT FROM PUBLISHER]