K. Iwatsuki

A 212 km NON-REPEATED TRANSMISSION EXPERIMENT AT 1.8 Gb/s USING LD PUMPED Er3+-DOPED FIBER AMPLIFIERS IN AN IM/DIRECT-DETECTION REPEATER SYSTEM

Over the past several years, non-repeated transmission distances using coherent detection have been longer than those using direct detection. It is noticed that minimum detectable photon numbers of the direct detection schemes are no more than those of the coherent schemes, under shot-noise limited condition. Optical amplification techniques play important roles to improve the receiver sensitivity in the direct detection system [1] and to increase the fiber launched power.

Super-dense WDM transmission of spectrum-sliced incoherent light for wide-area access network

This paper presents a detailed study on superdense wavelength-division multiplexing (WDM) transmission of spectrum-sliced incoherent light used for a wide-area access network. The transmission performance possible with this approach is evaluated numerically with regard to the following items: the transmission limit due to the chromatic dispersion, optimized signal-to-noise ratio design for the optical spectral width taking into account the adjacent-channel crosstalk, and the nonlinear effect generated by four-wave mixing at around the zero-dispersion wavelength. Superdense WDM transmission is also performed experimentally using 25-GHz channel-spaced, 15-GHz wide, up-to 156-Mb/s signals through up to 120 km of dispersion-shifted fiber.

80 Gb/s optical soliton transmission over 80 km with time/polarization division multiplexing

Time/polarization-division multiplexed optical solitons are successfully transmitted at 80 Gb/s over an 80 km dispersion-shifted single-mode-fiber. The 80 Gb/s optical pulse trains are generated by optically multiplexing 10 Gb/s gain-switched pulse trains. The transmitted solitons are demultiplexed with a polarization beam splitter and two intensity-modulators driven by a 10 Gb/s electrical timing recovery circuit. No error-rate floor is observed.<<ETX>>

160 Gb/s sub-picosecond transform-limited pulse signal generation utilizing adiabatic soliton compression and optical time-division multiplexing

0.8 ps TL pulses are successfully generated from a gain-switched DFB-LD by adiabatic soliton compression using a dispersion decreasing fiber (DDF). The compression ratio can be controlled using the peak input power into the DDF. We obtain a 10/spl times/2/sup n/ Gb/s pulse stream by optically multiplexing the compressed pulses with a Mach-Zehnder (MZ) interferometer type multiplexer, in which n can be freely selected from 1 to 4 by controlling the coupling ratios of the couplers in the MZ interferometers. By using the demonstrated techniques, we can multiplex the initial pulse stream up to 160 Gb/s at the noninterfering duty factor of 0.2.<<ETX>>

Adiabatic soliton compression of gain-switched DFB-LD pulse by distributed fiber Raman amplification

Using a dispersion-shifted single-mode fiber pumped by laser diodes as a distributed fiber Raman amplifier, the authors adiabatically compressed transform-limited (TL) pulses generated by a gain-switched distributed-feedback laser diode followed by linear compression and a spectral window. The initial TL pulses were successfully compressed asymptotically to almost pure solitons as short as 3.6 ps at the 2.4 dB total gain of a distributed fiber Raman amplifier, even without using solitons as the initial pulses. The experimental results are well supported by numerical calculations made with the beam propagation method.<<ETX>>

Picosecond laser diode pulse amplification up to 12 W by laser diode pumped erbium-doped fiber

Intense picosecond optical pulse generation from a gain-switched laser diode (LD) was demonstrated using a 1.48- mu m LD-pumped Er/sup 3+/-doped fiber laser amplifier. Saturation characteristics of the amplifier output power were also measured as a function of input repetition frequency. An amplified peak power of 12 W and 105-pJ pulse energy were obtained for 9-ps pulses at a 33-GHz repetition frequency. This is the highest peak power yet demonstrated in pulse generation employing all-laser diodes as active devices.<<ETX>>

20 Gb/s optical soliton data transmission over 70 km using distributed fiber amplifiers

20 Gb/s optical soliton data transmission is demonstrated over 70 km. Highly efficient distributed Raman amplifiers for fiber-loss compensation are realized by using high Delta n dispersion-shifted single-mode fibers pumped by laser diodes. To achieve high bit rate transmission, optical multiplexing and demultiplexing techniques are also employed. The bit error rate (BER) performance dependence on the input peak power of the optical pulse is measured. No power penalty can be seen at the input peak power required for transmitting optical solitons while the BER performance degrades when decreasing the input peak power.<<ETX>>

A quaternary amplitude shift keying modulator for suppressing initial amplitude distortion

This paper proposes a quaternary amplitude-shift-keying (4ASK) modulation circuit that suppresses amplitude distortion of the transmitting 4ASK signal. The performance of the proposed circuit is quantitatively verified through numerical calculation in comparison to a conventional alternative. The feasibility of the proposed circuit as integrated in a lithium niobate substrate is also demonstrated: the suppression of amplitude distortion is successfully demonstrated and minimum sensitivity of the transmitted 4ASK signal is 1.7 dB better than that offered by the conventional circuit.

Optical carrier supply module applicable to over 100 super-dense WDM systems of 1000 channels

This paper presents a prototype of an optical carrier supply module (OCSM) with a 12.5-GHz spaced 256-channel WDM carrier generator applicable to over 100 super-dense WDM systems and describes its scalability to 1000 channels.

3.6 Gb/s all laser-diode optical soliton transmission

3.6-Gb/s optical soliton transmission using a gain-switched 1.55- mu m distributed-feedback laser diode and a Ti:LiNbO/sub 3/ intensity modulator is demonstrated. An Er/sup 3+/-doped fiber amplifier and a Raman amplifier, both pumped by 1.48- mu m laser diodes, are used for achieving intense optical pulses and fiber-loss compensation, respectively. The intensity-modulation direct-detection optical receiver of a commercial F-1.6 G system is used to measure the bit-error rate.<<ETX>>