Repeater Spacing Research Articles

THREE INTEGRATED GAINS OF WIDE BANDWIDTH MULTI-PUMPING RAMAN OPTICAL AMPLIFIER: THE MAXIMUM FLATNESS

In the present paper, the performance of wide-bandwidth multi-pumping Ramanoptical amplifier employed in high-data rate and long-haul advanced opticalcommunication systems has been investigated under different pumping and fiberconditions. Raman gain is designed as straight line-exponential decay form withsmall flat maximum gain. Three different gains are defined and investigated.Multi-pumping number of NR pumps of equal pumping powers and differentpumping wavelengths of equal spacing are investigated. The pumps interactionsare reduced under large channel spacing.A novel software program is designed to handle the amplifier bandwidth as afunction of the controlling set of parameters. This broad bandwidth of maximumflatness is deeply analyzed. A wide range of the amplifier bandwidth of goodflatness is obtained up to 278 nm. It is found that higher gains and wide flatbandwidth can obtained if either the relative refractive index difference, ∆ or NRor the shift in Raman pumping wavelength, δλR or both of them increase.Thus, the repeater spacing in long-haul transmission cables designed for ultrawidewavelength division multiplexing (UW-WDM) can be adjusted for theemployed transmission channels.

MAXIMIZATION OF REPEATER SPACING USING MULTI-PUMPING RAMAN AMPLIFIER OF WIDE GAIN

In the present paper, maximization of repeater spacing has been investigated where multi-pumping Raman amplifier has been employed with equal pumping power and equal spacing pumping wavelength. The problem is cast into two coupled first order nonlinear differential equations taking into account both pump-pump interactions and signal-signal interactions along the fiber. These two equations are processed using simple but accurate software based on Runge-Kutta technique of the fourth order. The engagement of Raman amplifier and erbium doped fiber is processed. Wide gain of the amplifier is considered where two sets of a number of Raman pumps NR {5,10} are investigated. Raman pumping wavelength lR is over the range 1.42 £ lR, mm £ 1.52 and the channel wavelength ls is over the range 1.42 £ ls, mm £ 1.72. Two multiplexing techniques are processed in long-haul transmission cables where a number of channels up to 3600 in ultra-wide wavelength division multiplexing (UW-WDM) and a number of links up to 360 are handled in ultra-wide space division multiplexing (UW-SDM). The problem is investigated over wide ranges of affecting sets of parameters.

80-Gb/s error-free transmission over 5600 km using a cross absorption Modulation based optical 3R regenerator

Transoceanic transmission at 80 Gb/s was successfully demonstrated by introducing an optical retiming, reshaping, reamplifier (3R)-signal regenerator using cross-absorption-modulation gate and self-phase-modulation-based wavelength converter. At the 3R repeater spacing of 160 km, 80-Gb/s error-free transmission over 5600 km was achieved. The power penalty at 5600 km was 2 dB, and very clear eye-opening was observed even after 11 200-km transmission.

A simple design of a highly tolerable dispersion managed soliton system for trans-oceanic distance transmission

We present a design for a dispersion managed (DM) soliton system, which is based on two primary parameters; the dispersion compensation period (DCP), which is defined by the number of DSF spans between dispersion compensation fiber, and pulse width. We designed the optimum value of these two parameters to achieve the widest system margins for both repeater output power and signal wavelength for trans-oceanic distance transmission. We checked this analysis by experiments for both 10 and 20 Gb/s DM soliton systems having 53 km repeater spacing. Experimental results confirm the validity of proposed system design.

Benefit of Raman amplification in ultra-long-distance 40 Gbit/s-based WDM transmission using dispersion-flattened fibre span

The optimum configuration for hybrid Raman/EDFA amplification in ultra-long-distance 40 Gbit/s WDM transmission using a dispersion-flattened fibre span is investigated. By optimising the Raman gain, 16/spl times/40 Gbit/s WDM transmission over 2000 km was achieved with 80 km repeater spacing.

3.08 Tbit/s (77 × 42.7 Gbit/s) WDM transmission over 1200 km fibre with 100 km repeater spacing using dual C- and L-band hybrid Raman/erbium-doped inline amplifiers

3.08 Tbit/s (77 × 42.7 Gbit/s) WDM transmission over 1200 km fibre with 100 km amplifier spacing and 100 GHz channel spacing is demonstrated. Error-free transmission of all 77 channels is achieved by employing dual C- and L-band hybrid Raman/erbium-doped inline amplifiers, experimental low dispersion slope TrueWave® fibre, and forward error correction.

Theoretical analysis of system limitation for AM-DD/NRZ optical transmission systems using in-line phase-sensitive amplifiers

This paper shows the theoretically derived performance of single channel, amplitude modulation/direct detection optical transmission systems using in-line optical phase-sensitive amplifiers (PSA's). The calculations take into account the degradation of the signal-to-noise power ratio (SNR) and intersymbol interference (ISI) due to the distortion of transmitted signal pulses. The SNR is analyzed by considering not only amplifier noise and fiber loss but also noise enhancement by four-wave mixing in the transmission fiber. The ISI is estimated by eye-pattern degradation of the transmitted signal numerically calculated using the nonlinear Schrodinger equation. The regenerative repeater spacing of in-line PSA systems limited by SNR and ISI can be expanded by approximately 3 to 10 times that of in-line EDFA systems, in the case of |D|/spl les/0.1 ps/mn/km dispersion fiber systems transmitting a 40-Gb/s signal.

Long-span repeaterless transmission systems with optical amplifiers using pulse width management

This paper proposes pulse width management in order to extend the repeater spacings of repeaterless transmission systems with optical amplifiers. First, the dependency of receiver sensitivity on duty ratio, receiver response, and fiber dispersion is clarified by numerical analysis. Next, the calculation results of sensitivity as a function of signal format and receiver basedband response are verified experimentally. Moreover, we show that pulse width management which uses return-to-zero (RZ) format with large duty ratio (/spl sim/0.7) at the transmitter and pulse compression at the receiver increases the repeater gain by /spl sim/4.5 dB compared to conventional systems employing nonreturn-to-zero (NRZ) format. Record repeater spacing of 300 km is realized at 10 Gb/s by utilizing pulse width management.

240-km repeater spacing in a 5280-km WDM system experiment using 8 x 2.5 Gb/s NRZ transmission

A repeater spacing of 240 km was experimentally demonstrated over a distance of 5280 km in an 8/spl times/2.5 Gb/s wavelength-division-multiplexing (WDM) transmission experiment. This long-span length was achieved by a combination of Raman amplification, a locally pumped erbium-doped fiber (EDF), and two remotely pumped EDFs. The total gain obtained from those four gain elements was about 50 dB. The performance demonstrated in this experiment was comparable to that of a system of similar length and capacity using conventional erbium-doped fiber amplifier (EDFA) technology at a repeater spacing of 80 km.

Scale of WDM transport network using different types of fibers

This paper describes a statistical calculation method for transmission limits taking into consideration dispersion-shifted fiber (DSF) zero-dispersion wavelength deviation for wavelength division multiplexing (WDM) systems employing unequal channel spacing. For example, the upper limit of fiber input power achieving a bit error rate (BER) less than 10/sup -12/ shows a 3 dB improvement when the standard deviation is increased from 1 to 8 nm when the transmission distance with a 80 km repeater spacing is 640 km. Furthermore, the network scales employing 1.55 /spl mu/m DSF, nondispersion-shifted fiber (N-DSF) and conventional single-mode fiber (SMF) are shown. Finally, a method for estimating the transmission limit for a receiver with different sensitivity, different node architecture, and different bit rates is described.

Error-free operation of in-line phase-sensitive amplifier

Optical phase-sensitive amplifiers (PSAs) are promising circuit elements for expanding the regenerative repeater spacing of optical transmission systems. The authors first demonstrate error-free operation of in-line PSAs with a 10 dB net gain by using an injection-locked pump with a compensation phase-locked loop.

Dispersion limits in 10-Gb/s standard fiber systems using nonlinear optoelectronic repeaters

We investigate the dispersion limited transmission distance in 10-Gb/s standard fiber networks which use analog nonlinear optoelectronic repeaters at 1.55 /spl mu/m. The simulations show that the maximum transmission distance in such a system can be around 1000 km for a repeater spacing of 30 km. If the electrical signal is inverted in each repeater, it is possible to increase the repeater spacing without degrading the performance or to increase the maximum transmission distance.

10 Gbit/s eight-channel transmission experiment over 480 km with 120 km repeater spacing using orthogonal polarisation arrangement and bit-phase arranged RZ pulse format

The authors show the feasibility of a 10 Gbit/s eight-channel multi-repeater transmission system using 1.55 /spl mu/m dispersion shifted fibres. Transmission over 480 km with 120 km long repeater spacings is achieved using an orthogonal polarisation arrangement and bit-phase arranged RZ pulse format.

Linear and nonlinear dispersion compensation of short pulses using midspan spectral inversion

Fiber nonlinearity and dispersion may limit the repeater spacing in high speed fiber-optic transmission systems. We report experimental and numerical results on the nonlinear propagation of short optical pulses over standard nondispersion shifted fiber links which are dispersion compensated using midspan spectral inversion. It has been found that an increased transmission nonlinearity can be tolerated if the spectral inversion is moved away from the midpoint of the span. Full recovery of the initial pulsewidth is experimentally demonstrated in the presence of nonlinearities. A system design based on these results is presented, allowing high transmitted power and long repeater spacing.

System performance evaluation of the FSA submarine optical amplifier system

The FSA submarine optical amplifier system developed for commercial use is designed to transmit 2.5 and 10 Gb/s signals flexibly; its repeater spacing is 90 km. It contains six line pairs to yield a maximum transmission capacity of 60 Gb/s. Its system configuration, and the characteristics of its fibers and optical amplifiers, which realize effective dispersion and optical passband management, are introduced. We discuss its performance with regard to the parameters significant in optically amplified transmission: evolution of zero dispersion wavelength (ZDW), polarization mode dispersion (PMD), and fiber nonlinearity induced impairments. Signal-to-noise ratios (SNR's) for 2.5 and 10 Gb/s signal transmission are measured and the improvements offered by polarization scrambling are also discussed. Finally, ZDW, PMD, and SNR characteristics of the system after installation are reported.

Stimulated brillouin scattering threshold representing bit‐error ratio degradation in single‐mode optical fiber transmission

AbstractAchieving maximum repeater spacing in optical fiber transmission systems is compromised by the input power limit due to stimulated Brillouin scattering (SBS). In digital transmission, SBS causes bit‐error rate degradation. The calculation method for the SBS equation under steady state in a single‐mode optical fiber has been established here; boundary conditions and actual environment are both considered. A new SBS threshold has been proposed as the input optical power at which the backscattered SBS power equals the Rayleigh backscattering power at the fiber input end. Based on a detailed comparison with experimental results, it has been confirmed that the proposed threshold expresses accurately the bit‐error rate degradation due to the SBS; it is approximately 2.5 dB lower than the conventional threshold. Use of the proposed threshold makes accurate system design possible.

Design and performance of the fsa submarine optical amplifier system

AbstractThe FSA submarine optical amplifier system (submarine fiber using optical amplifiers) has been developed. It can transmit signals up to 10 Gbit/s with a repeater spacing of 100 km. The submarine repeaters contain optical amplifiers for six line pairs to yield a maximum capacity of 60 Gbit/s. This paper describes its system configuration, the repeater configuration, and the fiber dispersion management scheme used to realize bit‐rate flexible transmission and in‐service monitoring.In long‐haul optical amplifier systems, since the amplified spontaneous emission noise from the optical amplifier is the main impairment limiting the transmission distance, an SNR design technique that takes this noise into account is developed. Finally, the results obtained after the commercial installation of this system in the Kagoshima‐Okinawa route (total length 905 km) are reported, including chromatic dispersion characteristics and SNR values at both 2.5 Gbit/s and 10 Gbit/s transmission. The effectiveness of the system design is verified through the demonstration of good transmission performance and the feasibility of in‐service monitoring.

High-accurate fault location technology using FSK-ASK probe backscattering reflectometry in optical amplifier submarine transmission systems

This paper proposes a new modulation format for optical time domain reflectometry (OTDR) to eliminate optical surge and improve OTDR performance in optical amplifier submarine transmission systems. The modulation format, FSK-ASK, uses a short high-power probe pulse and a long dummy pulse. Thanks to the slow gain dynamics of erbium-doped fiber amplifiers, both pulses experience an identical gain, equal to the loss of a span, so that the probe pulse maintains its high power and does not develop into an optical surge. Fault location experiments verify a theoretical prediction that FSK-ASK improves the signal-to-noise ratio (SNR) of OTDR by an amount as large as the power ratio of the probe to dummy signal. They also confirm the elimination of the optical surge caused by conventional OTDR using a solitary probe pulse. An FSK-ASK OTDR is applied in a commercial submarine amplifier transmission system which has a total transmission length of 890 km and a repeater spacing of 90 km. These field trial results show that subtle fiber anomalies can be located, with a spatial resolution of 1 km, along the entire length of the amplifier transmission system from a terminal end.

10 Gbit/s × 10 channel transmission experiment over 600 km with 100 km repeater spacing employing cascaded fluoride-based erbium doped fibre amplifiers

A 10 Gbit/s 10 channel transmission experiment with 100 km repeater spacing (23 dB fibre loss) is demonstrated with 600 km dispersion shifted fibre. Transmission was successfully performed by employing fluoride-based erbium doped fibre amplifiers and unequal channel spacing allocation.

2.5 Gbit/s-9720 km, 10 Gbit/s-6480 km transmission in the FSA commercial system with 90 km spaced optical amplifier repeaters and dispersion-managed cables

The authors report 2.5 and 10 Gbit/s transoceanic distance transmission in a commercial FSA optical amplifier system which has 90 km repeater spacing. The unique fibre dispersion management technique and amplifier passband management scheme used in the system are successfully demonstrated. The SNR improvement achieved with polarisation scrambling is also reported.