Corrado Dragone

An N*N optical multiplexer using a planar arrangement of two star couplers

The author describes the design of an integrated N*N multiplexer capable of simultaneously multiplexing and demultiplexing a large number (up to about 50) of input and output wavelength channels. The multiplexer is a generalization of the 2*2 Mach-Zehnder multiplexer. It consists of two N*M star couplers connected by M paths of unequal length. Aberrations caused by mutual coupling in the waveguide arrays are minimized by a correction scheme that causes each star coupler to accurately perform a Fourier transformation. The multiplexer should be useful as a wavelength routing device for long haul and local area networks.<<ETX>>

A wavelength-division multiplexed passive optical network with cost-shared components

We demonstrate a passive optical network (PON), based on a wavelength-division multiplexing router, with modulators (instead of lasers) at the subscriber terminals. A single, cost-shared, tunable laser is time-division multiplexed to provide bidirectional switched WDM services for N subscribers with independent formats and bit-rates for each. Simultaneous support of telephony and compressed digital video are presented in which RF subcarrier multiplexing is used to provide service segregation and resolve upstream packet contention.<<ETX>>

Integrated optics N*N multiplexer on silicon

The authors report the measured performance of an integrated N*N multiplexer fabricated using SiO/sub 2//Si waveguides. The insertion loss for N=7 was typically lower than 2.5 dB, and crosstalk was less than -25 dB. The multiplexer response is approximately periodic. In each period the multiplexer accepts, from each input waveguide, a total of N channels, and it efficiently transmits each channel to a particular output port. Similarly, each output port receives N channels, one from each input port. Thus, the total number of channels that can be transmitted simultaneously is N/sup 2/, which requires N optical frequencies.<<ETX>>

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications.

Ideal microlenses for laser to fiber coupling

The design and fabrication of ideal microlenses for semiconductor laser to fiber coupling are reported. Properly coated for reflections, lenses of the new design can theoretically collect 100% of the radiated energy of a modal-symmetric laser source. The crucial feature is its hyperbolic shape. Microlenses fabricated directly on the end of the fiber by laser micromachining have demonstrated up to 90% coupling efficiency. This performance represents a major advance in microlens technology when compared to currently fabricated hemispherical microlenses which are at best 55% efficient. A theoretical comparison of the two lens shapes illuminates the advantages of the hyperbolic profile. The ability to couple all of the light from a semiconductor laser into a fiber has far-reaching implications for all optical communication systems. >

LARnet, a local access router network

A novel local access network, LARNet, is proposed and demonstrated. A multifrequency laser, whose wavelength COMB94 is matched to that of a passive waveguide router in the remote node, is used as a downstream signal source. A 1.3-/spl mu/m commercially available LED provides the upstream signal. LARNet solves a major problem of WDM networks, the spectral alignment between the optical wavelengths of different channels. Furthermore. The expensive components are shared among all subscribers. Our measurements indicate that aggregate rates of 2 Gbps downstream and 155 Mbps upstream are feasible.<<ETX>>

Efficient N*N star couplers using Fourier optics

A technique for constructing an efficient N*N star coupler with large N at optical frequencies is described. The coupler is realized in free space using two arrays, each connected to N single-mode fibers. The highest efficiencies are obtained using a planar arrangement of two linear arrays separated by a dielectric slab serving as free-space region. The coupler is suitable for mass production in integrated form, with efficiencies exceeding 35%. >

A 16*1 wavelength division multiplexer with integrated distributed Bragg reflector lasers and electroabsorption modulators

The integrated operation of a 16*1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber.<<ETX>>

Demonstration of a 15*15 arrayed waveguide multiplexer on InP

By interconnecting two star couplers with a waveguide grating, the authors built a monolithic 15*15 multiplexer on InP. The grating order of 148 gives a free spectral range of 10.5 nm (1.3 THz) and a channel spacing of 0.7 nm (87 GHz) at 1550 nm wavelength. A crosstalk between adjacent channels of less than 18 dB and a residual crosstalk of less than 25 dB were obtained. The on-chip insertion loss is typically 2-4 dB.<<ETX>>

Broad-band array multiplexers made with silica waveguides on silicon

A waveguide array multiplexer design that is particularly suitable for making broadband low-order devices is presented. Two-channel multiplexers at 1.0-1.55 mu m, 1.31-1.53 mu m, and 1.47-1.55 mu m are demonstrated. Compared to conventional waveguide multiplexers, these devices have wide spectral ranges of low crosstalk. The devices are polarization independent. The crosstalk and fiber-to-fiber insertion loss for the 1.31-1.53 mu m multiplexer were about -35 and -2 dB, respectively. >