Noboru Takachio

Optical carrier supply module using flattened optical multicarrier generation based on sinusoidal amplitude and phase hybrid modulation

This paper presents an optical carrier supply module (OCSM) that functions as a common multicarrier light source, a wavelength bank, for superdense wavelength-division multiplexing (SD-WDM) networks that utilize a large number of wavelengths with narrow channel spacing. A novel sideband generator based on a sinusoidal amplitude-phase hybrid modulation scheme is the key technique. The sideband generator generates nine flattened optical sidebands within 3 dB from one seed light source, and the input from wavelength-division multiplexing (WDM) seed carriers expands the number of generated sidebands. Scalability against the number of wavelengths is achieved by increasing the number of seed carriers used. The SD-WDM system employing OCSM reduces the number of laser diodes (LDs) and attendant wavelength monitoring/stabilization circuits. Multiple distributions to SD-WDM networks by splitting the OCSM output can promote this effect. We designed OCSM and experimentally investigated its performance pertaining to the electrical signal-to-noise ratio (SNR) of the OCSM output. The experimental results show the wavelength scalability to 1000 channels. We also developed an OCSM prototype that generated 12.5-GHz-spaced 256-channel WDM carriers. All the generated carriers exhibit the electrical SNR of more than 31.5 dB at 2.5 Gb/s and the power flatness of within 3 dB. The distribution over 100 SD-WDM networks is experimentally confirmed.

Optical signal quality monitor using direct Q-factor measurement

In photonic networks, different types of signal formats such as synchronous digital hierarchy, plesiochronous digital hierarchy, and synchronous optical network are included. Therefore, an optical signal-quality monitoring scheme that is independent of the signal format is indispensable. This letter proposes a novel scheme to accomplish this. This method derives the standard deviation and the mean value of the marks/spaces rail of an eye pattern, and calculates the Q-factor. Computer simulation results confirm the applicability of the new technique.

1-Tb/s (100 x 10 Gb/s) super-dense WDM transmission with 25-GHz channel spacing in the zero-dispersion region employing distributed Raman amplification technology

We achieve 1 Tb/s (100/spl times/10 Gb/s) super-dense WDM (super DWDM) transmission with 25-GHz channel spacing (0.4 bit/s/Hz spectral efficiency) in the zero-dispersion region over a 4/spl times/80 km dispersion-shifted fiber by employing backward pumped distributed Raman amplification and forward error correction. By adopting bi-directional pumping, we present experimental results showing that the transmission distance is extended approximately threefold to 1040 km.

12.5 GHz spaced 1.28 Tb/s (512-channel x 2.5 Gb/s) super-dense WDM transmission over 320 km SMF using multiwavelength generation technique

We achieve a 512-channel super-dense wavelength-division-multiplexing (WDM) transmission with a 12.5 GHz channel spacing over 320 km (80 km/spl times/4) of standard single-mode fiber in the C+L-bands. Optical carrier supply modules, which are based on a flattened sideband generation scheme, are applied to generate the 512 wavelengths from only 64 distributed-feedback laser diodes with a frequency spacing of 100 GHz. Arrayed-waveguide gratings with a 12.5 GHz spacing are used in this super-dense WDM experiment.

22 x 10 Gb/s WDM transmission based on extended method of unequally spaced channel allocation around the zero-dispersion wavelength region

This letter proposes all unequally spaced channel allocation method that increases the number of channels around the zero-dispersion wavelength region. The validity of this method is confirmed by numerical simulation considering the fluctuation of the zero-dispersion wavelength existing along the installed 1.55-/spl mu/m dispersion-shifted fibers (DSFs). A 22/spl times/10 Gb/s transmission experiment over 320 km of DSF using the wavelengths ranging from 1532 to 1562 nm is successfully conducted by employing this method.

Application of Raman-distributed amplification to WDM transmission systems using 1.55-/spl mu/m dispersion-shifted fiber

A numerical design method for wavelength division multiplexing (WDM) transmission systems employing distributed Raman amplification (DRA) is proposed. This method evaluates fiber nonlinear effects by considering the equivalent fiber loss with DRA. The method is used to evaluate the performance of WDM transmission systems in which DRA is employed in a 1.55-/spl mu/m dispersion-shifted fiber (DSF) transmission line. Transmission limit and the optimum fiber input powers for 1550-nm band (C-band) and 1580-nm band (L-band) transmission are investigated. Results show that bidirectional pumping is the best approach to extending transmission distance. Furthermore, the transport limits of optical transport networks that use DRA and optical add/drop multiplexers are analyzed.

Dynamic gain control by maximum signal power channel in optical linear repeaters for WDM photonic transport networks

The concept of a dynamic gain control method that automatically selects the maximum signal power and keeps it constant is described. This method can cope with not only changes in the number of channels, but also signal power fluctuations. No specific control channel is needed and gain control is active as long as just one signal channel is present. This methods feasibility is confirmed by eight-channel WDM power transient measurements.

An optical 90/spl deg/-hybrid balanced receiver module using a planar lightwave circuit

An optical 90/spl deg/-hybrid coherent receiver module is constructed that uses the planar lightwave circuit technique. The module consists of an optical 90/spl deg/-hybrid silica planar waveguide and two 14 GHz balanced O/E converters; the solder-bump technique is employed. For both sets of paths between the optical coupler and the twin-p-i-n photodetector pairs, the effective propagation time differences were reduced to within 4 ps. A 10 Gb/s BPSK homodyne detection experiment confirms the feasibility of the receiver.<<ETX>>

Power excursion suppression in cascades of optical amplifiers with automatic maximum level control

The automatic maximum level control scheme, which automatically selects the maximum power channel as the control channel and keeps its maximum power constant, is the most attractive candidate among gain control techniques applicable to wavelength-division-multiplexed linear repeaters. The design guidelines of this scheme are presented. The power transient response and bit-error-rate performance of the remaining channels during changes in the number of channels are measured in cascades of four repeaters. It is experimentally confirmed that power excursions and power penalties at the bit-error rate of 10/sup -9/ can be suppressed to less than 0.7 dB and less than 0.3 dB, respectively, even when seven out of eight channels are dropped within 1 /spl mu/s.

A new packaging technique for an optical 90/spl deg/-hybrid balanced receiver using planar lightwave circuits

A new packaging technique for an optical 90/spl deg/-hybrid balanced receiver using planar lightwave circuits (PLC) has been developed for optical frequency division multiplexing (OFDM). This receiver consists of a silica-based PLC for an optical coupler and two polarization beam splitters (PBS), two GRIN rod lenses to achieve perfect optical interconnection, and two photoreceivers each having a preamplifier and twin PIN-PDs. The photoreceivers use the microsolder bump technique to eliminate the parasitic elements of the interconnections between the preamplifier and the twin PIN-PDs, and the impedance-matched film carrier technique to achieve impedance-matched interconnection between the preamplifier and the ceramic package. This receiver achieved a broadband frequency response of 14 GHz, and, consequently, 10-Gbit/s homodyne detection. The experiments showed that a receiver fabricated with our new packaging technique has excellent performance.