Investigation of 43-Gb/s Transmission With a Wavelength Preserving SOA-Based Optical Regenerator

Transmission with cascaded optical regeneration based on synchronous modulation combined with optical reshaping by cross-gain compression in a semiconductor optical amplifier is investigated at 43 Gb/s over transoceanic distances (10 000 km). The proposed optical regenerator configuration performs signal reshaping and retiming while preserving the input signal wavelength. The regenerator cascadability properties are investigated using a reconfigurable loop to assess the impact of different inter-regeneration spacing on the transmission signal properties.      

1.3-μm Pr-doped In-Ga-based fluoride fiber amplifiers pumped bygrating-fiber-pigtailed 0.98-μm-band laser diodes with a detunedwavelength of 1 μm

At most efficient pump wavelength, a praseodymium-doped In-Ga-based fluoride fiber is directly pumped by four 0.98-μm-band laser diodes. These lasing wavelengths are detuned from 0.98 to 1 μm by external selective optical feedback from fiber grating reflectors. Maximum signal output power of +13.5 dBm is obtained at 1.296 μm. Four-wavelength multiplexed signals at 1.296-1.311 μm are amplified with a deviation of gain less than 1.9 dB. By using the amplifier as a power booster, data of 2.5 Gb/s is successfully transmitted more than 100 km     

1.52-1.59-μm range different-wavelength modulator-integratedDFB-LDs fabricated on a single wafer

We report for the first time different-wavelength modulator-integrated distributed-feedback laser diodes (DFB/MODs) fabricated on a single wafer, whose lasing wavelength cover almost all of the expanded erbium-doped fiber amplifier (EDFA) gain band from 1.527 to 1.593 μm. The devices provided uniform and high-performance characteristics such as a threshold current less than 12 mA and successful transmission of 2.5 Gb/s-600 km through a normal fiber     

10-Gb/s optical transmission up to 253 km via standard single-modefiber using the method of dispersion-supported transmission

Using the new method of dispersion-supported transmission, 10 Gb/s signals at 1.53 μm wavelength are transmitted on standard single-mode fiber with zero dispersion at 1.3 μm via the record length of 253 km without in-line regeneration. Detailed experiments with a directly modulated laser demonstrate the system performance for different fiber lengths ranging from 0 up to 253 km     

1.55 μm, 2.5 Gb/s direct detection repeaterless transmission of160 km nondispersion shifted fiber

A repeaterless transmission experiment through 160 km of non-dispersion-shifted fiber at bit rate of 2.5 Gb/s is reported. A direct-current-modulated distributed-feedback laser in conjunction with an erbium-doped fiber amplifier for power amplification constitute the transmitter. The regenerator includes the conventional APD photodetector and the subsequent amplifiers and timing recovery circuit. With careful decision level and laser bias adjustment, less than 0.6 dB of overall system degradation is incurred in this simple system configuration     

Chromatic dispersion compensation in coherent opticalcommunications

Chromatic dispersion compensation techniques in coherent transmission systems are reviewed and discussed for potential feasibility. The key compensation device is the wideband delay equalizer. It is shown that stripline-type delay equalizers have the potential for compensating distortion up to 10 Gb/s using a conventional 1.3-μm zero-dispersion single-mode fiber at 1.5 μm. Chromatic dispersion is successfully compensated with a stripline delay for CPFSK transmission at 4 and 6 Gb/s over 200 km of 1.3-μm zero-dispersion single-mode fiber at 1.55 μm. The bandwidth requirement of the compensation techniques for heterodyne detection is more than 10 GHz. However, it is difficult to realize such broadband receivers. Therefore, phase diversity detection with dispersion compensation is a promising scheme     

High performance selectively oxidized VCSELs and arrays forparallel high-speed optical interconnects

High-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operate at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. To enhance fundamental single-mode emission for larger devices of reduced series resistance a surface relief transverse mode filter is employed. Fabricated VCSELs are applied in various interconnect schemes. InGaAs quantum-well based VCSELs at 935 nm emission wavelength are investigated for use in perfluorinated graded-index plastic-optical fiber (GI-POF) links. We obtain a 7 Gb/s pseudo random bit sequence (PRBS) nonreturn-to-zero (NRZ) data transmission over 80 m long 155 μm diameter GI-POF. We investigate data transmission over standard 1300 nm, 9 μm core diameter single-mode fiber with selectively oxidized single-mode GaAs and InGaAs VCSELs. We achieve biased 3 Gb/s and bias-free 1 Gb/s pseudo-random data transmission over 4.3 km at 830 nm emission wavelength where a simple fiber mode filter is used to suppress intermodal dispersion caused by the second order fiber mode. For the first time, we demonstrate 12.5 Gb/s data rate transmission of PRBS signals over 100 m graded-index multimode fiber or 1 km single-mode fiber using high performance single-mode GaAs VCSELs of 12.3 GHz modulation bandwidth emitting at λ=850 nm     

Pseudomorphic 2DEG FET IC's for 10 Gb/s optical communicationsystems with external optical modulation

An optical modulator driver IC and a preamplifier IC for 10 Gb/s optical communication systems are developed using AlGaAs/InGaAs/GaAs pseudomorphic two-dimensional electron gas (2DEG) FETs with a gate length of 0.35 μm. The optical modulator driver IC operates at a data rate up to 10 Gb/s with an output voltage swing of more than 4 V_p-p . The bandwidth for the amplifier IC is 13.0 GHZ with ab 47 dB-Ω transimpedance gain. In addition, optical transmission experiments with external optical modulation using these ICs have successfully been carried out at 10 Gb/s     

Optically amplified first window systems experiments

A diode pumped, commercially packaged, thulium doped fluoride fiber amplifier (TDFFA) operating in the region of 0.8 μm has been characterized. The unit is capable of producing large small signal gains, low noise figures and high saturated output powers. A power amplifier slope efficiency of 62% has been achieved at 810 nm. The same TDFFA unit was used in a series of systems experiments, at data rates of 310 Mb/s and 1.2 Gb/s, in the first telecommunications window. The results of this work indicate that data can be transmitted over ≈10 km lengths of both singlemode and standard transmission fiber, while still allowing significant margin to split the signal to a number of customers. The application of the TDFFA could therefore have significant benefit for future LAN/MAN type systems architectures involving large signal splits to customer's premises     

Cascadability of an All-Optical 3R Regenerator Utilizing Nonlinear Phase Modulation and Offset Filtering at 10 and 40 Gb/s

The cascadability of a polarization-insensitive wavelength-preserving all-optical 3R regenerator is experimentally investigated for bit rates of 10 and 40 Gb/s. The regenerator consists of a self-pulsating laser for clock recovery, cross-phase-modulation-based retiming, and self-phase-modulation-based reshaping. A recirculating loop is used to demonstrate the cascadability of the regeneration scheme by transmitting return-to-zero on–off-keyed signals over 18 000 km at 10 Gb/s and over 8000 km at 40 Gb/s.      

Optimum index profile of the perfluorinated polymer-based GIpolymer optical fiber and its dispersion properties

The significant advantages in bandwidth and low material dispersion of perfluorinated (PF) polymer-based graded-index polymer optical fiber (GI POF) are theoretically and experimentally reported for the first time. It is confirmed that the low attenuation and low material dispersion of the PF polymer enables 1 Gb/s km and 10 Gb/s km transmission at 0.85-μm and 1.3-μm wavelengths, respectively. The PF polymer-based CI POF has very low material dispersion (0.0055 ns/nm·km at 0.85 μm), compared with those of the conventional PMMA-based POF and of multimode silica fiber (0.0084 ns/nm km at 0.85 μm). Since the PF polymer-based GI POF has low attenuation from the visible to near infrared region, not only the 0.65-μm wavelength which is in the low attenuation window of the PMMA-based GI POF, but other wavelengths such as 0.85-μm or 1.3-μm etc. can be adopted for the transmission wavelength. It is clarified in this paper that the wavelength dependence of the optimum index profile shape of the PF polymer-based GI POF is very small, compared to the optimum index profile shape of the silica-based multimode fiber. As a result, the PF polymer-based GI POF has greater tolerance in index profile variation for higher speed transmission than multimode silica fiber. The impulse response function of the PF polymer-based GI POF was accurately analyzed from the measured refractive index profile using a Wentzel, Kramers, Brillouin (WKB) numerical computation method. By considering all dispersion factors involving the profile dispersion, predicted bandwidth characteristic of the PF polymer-based GI POF agreed well with that experimentally measured     

2.24-Gbit/s 151-km optical transmission system using high-speedintegrated silicon circuits

Optical transmission experiments performed at 2.24 Gb/s using standard single-mode fiber with dispersion zero at 1.3 μm are discussed. In the optical transmitter, a 1.5-μm-wavelength distributed feedback laser is directly modulated by means of a special electrical drive pulse shaping technique. A link length of up to 151 km is bridged. This is the longest repeater distance at 2 Gb/s using direct detection without optical amplifiers reported so far. Moreover, the transmission system includes multiplexing and demultiplexing equipment using specially developed high-speed silicon integrated circuits. The whole system is assembled in a version suitable for field trial applications     

Modulator driver and photoreceiver for 20 Gb/s optic-fiber links

Two integrated circuits, a modulator driver and a photoreceiver integrating a metal-semiconductor-metal (MSM) photodetector, a differential transimpedance amplifier and two limiting amplifier stages for high-speed optical-fiber links are presented. The IC's were manufactured in a 0.2 μm gate-length AlGaAs-GaAs high-electron mobility transistor (HEMT) technology with a f_T of 60 GHz. The modulator driver IC operates up to 25 Gb/s with an output voltage swing of 3.3 V_p-p at each output. The 1.3-1.55 μm wavelength monolithically integrated photoreceiver optoelectronic integrated circuit (OEIC) has a bandwidth of 17 GHz with a high transimpedance gain of 12 kΩ. Eye diagrams are demonstrated at 20 Gb/s with an output voltage of 1 V_p.p     

Two-Stage SPM-Based All-Optical 2R Regeneration by Bidirectional Use of a Highly Nonlinear Fiber

Two-stage all-optical 2R (reamplification and reshaping) signal regeneration based on spectrum broadening due to self-phase modulation in a nonlinear fiber and subsequent off-centered filtering is demonstrated by the use of only one fiber spool in which the signal is transmitted twice in opposite directions. The two-stage configuration allows wavelength shift-free operation of the regenerator. Recirculating-loop signal transmission and regeneration experiment shows that the bidirectional 2R regenerator extends transmission distance by a factor more than two for an unequally-spaced 40 Gb/s short-pulse train with minimum pulse separation of 12.5 ps. Numerical simulation for assessing the influence of Rayleigh backscattering in the bidirectional configuration is performed, which shows that although some influence of Rayleigh backscattering can appear at higher operation speeds such as 80 Gb/s, strong noise reduction is still achievable by the bidirectional two-stage regeneration.      

A Si-bipolar technology for optical fiber transmission rates above10 Gb/s

A multiplexer operating at up to 12 Gb/s has been demonstrated using a simple, but optimized, silicon bipolar technology with 2 μm lithography. Using this simple but optimized technology, a 12 Gb/s multiplexer was implemented. Circuit simulations predict the increase of the bit rate up to at least 15 Gb/s by changing to the 1.5 μm lithography. The results of experimental investigations and circuit simulations show that low-cost silicon-based bipolar circuits will be available for future optical-fiber transmission systems with data rates higher than 10 Gb/s     

Simultaneous amplification of 20 channels in a multiwavelengthdistribution system

Simultaneous amplification of a 20-channel multiwavelength signal using a traveling-wave semiconductor optical amplifier is discussed. The channels occupied a band 34 nm wide centered at 1.54 μm, and 6-8-dB net gains were obtained. Bit-error-rate measurements at 1 Gb/s showed small receiver penalties due to amplifier noise and interchannel crosstalk     

401 km, 622 Mb/s and 357 km, 2.488 Gb/s IM/DD repeaterlesstransmission experiments using erbium-doped fiber amplifiers and errorcorrecting code

Record repeaterless transmission distances of 401 km at 622 Mb/s and 357 km at 2.488 Gb/s on nondispersion-shifted fiber are demonstrated. The transmission format is intensity modulation/direct detection (IM/DD), and a forward error correcting code scheme is implemented. Erbium-doped fiber amplifiers are used at the transmit and receive end of the system as postamplifier, preamplifier, and remotely pumped amplifier     

1 Gbit/s PSK homodyne transmission system using phase-lockedsemiconductor lasers

Homodyne detection of 1 Gb/s pilot-carrier (BPSK) optical signals using phase-locked 1.5 μm external-cavity semiconductor lasers is discussed. After 209 km fiber transmission of a 2¹⁵-1 pseudorandom binary sequence (PRBS), the measured receiver sensitivity is 52.2 dBm or 46 photons/bit. Experimental evidence of the data-to-phase-lock crosstalk that potentially limits the usable ratio of linewidth to bit rate in pilot-carrier PSK homodyne systems is presented     

40G比特/秒 FSK传输链接的理论和实证研究

A novel Frequency Shift Keying (FSK) transmitter that can operate at 40Gb/s and above is proposed. The transmission characteristics of a FSK signal at 40Gb/s are investigated under varying dispersion management. The resilience of compensation ratio and power level is obtained. We also experimentally demonstrate transmission over 100km SMF and transparent wavelength conversion based on a semiconductor optical amplifier.     

Compensation of dispersion in optical fibers for the 1.3-1.6 μmregion with a grating and telescope

The transmission of ultrashort optical pulses over long distances in optical fibers is limited by pulse broadening due to group velocity dispersion. A grating and telescope dispersion compensator with group velocity dispersion of equal magnitude and opposite sign can compensate for the fiber dispersion. The possible benefits of such dispersion compensation in the 1.3-1.6-μm wavelength region are investigated. The results show that compensation of first-order dispersion at 1.55 μm in a fiber with zero dispersion near 1.3 μm is primarily limited by the second-order dispersion of the grating and the telescope compensator. For a wavelength slightly greater than the zero dispersion wavelength, both the first- and second-order group velocity dispersion can be canceled by the grating and telescope dispersion compensator, allowing transmission exceeding 100 Gb/s over 100 km