Parallel Optical Transmission Research Articles

Ten-channel optical transmitter module for sub-system interconnection operating at λ=1.3 μm up to 12.5 Gbit/s

Parallel optical interconnection devices feature wide bandwidth, low loss and cross-talk, small size and weight along with low power consumption and cost. They appear particularly suitable to replace the electrical interconnections wherever high connection density and transmission capacity are required (e.g., in board-, cabinet-, and building interconnections). We report on a 10-channel parallel optical transmitter module with a 12.5 Gbit/s total bit-rate. The module includes a commercial 10-channel Fabry-Perot laser array chip) emitting at /spl lambda/=1.3 /spl mu/m, coupled to a standard 50/125 /spl mu/m multimode fiber ribbon, and a silicon CMOS laser driver IC. The IC allows low power consumption even at the high bit-rate achieved, and therefore requires only a passive thermal management, contributing to lower the costs. The output optical power of both logicall 0 and 1 levels can be adjusted externally. The module operates up to 1.25 Gbit/s/ch, exhibiting at a bit error ratio (BER) better than 10/sup -14/. With a power budget of more than 10 dB and a power consumption of 130 mW per channel. An interconnection distance in excess of 1200 m has been demonstrated, with a residual power margin of 4 dB without BER degradation. In this way our transmitter gives interconnection distances in excess of 500 m, not attainable with the shorter wavelengths given by surface emitters, and permits low power dissipation (low threshold light source and CMOS circuits) and low cost fabrication. Such characteristics make the module interesting for applications in which medium-long distances are involved and high bit-rates required, but reduced power consumption and dimensions are mandatory, as for interconnections between submodules in the large switching nodes of new generation.

Space-CDMA based 2D parallel optical transmissionover record length (100 mlong) image fibre

Space code division multiple access (CDMA) based 2D parallel optical transmission over a record length (100 m long) image fibre is demonstrated. Four 2 × 2 bit-planes encoded by 8 × 8 signature patterns are multiplexed and transmitted over a 100 m long image fibre. Each receiver can regenerate an intended bit-plane by optically correlating the received signal with the corresponding signature pattern. This opens up the application to high throughput massively parallel processor data links.

Skew-free parallel optical transmission systems

This paper proposes two kinds of parallel line codes based on multiplexing and nonmultiplexing, and a method of automatic skew suppression based on bit synchronization and frame synchronization. This achieves parallel high-speed optical transmission to overcome bottlenecks in parallel electronic transmission and to increase the distance of high-throughput interconnections. We have developed GaAs coder/decoder large-scale integrations (LSIs) for the coding algorithm and skew suppression, and analog LSIs for compact, low-power, highspeed parallel optical links. Experimental results show that our proposed parallel transmission methods and fabricated LSIs can play a key role in realizing high-speed, long-distance parallel transmission and in reducing the size and power consumption of high-throughput parallel optical links.

A two-dimensional optical parallel transmission using a vertical-cavity surface-emitting laser array module and an image fiber

The possibility of high-density optical parallel transmission using an arrayed vertical-cavity surface-emitting laser (VCSEL) and an image fiber was demonstrated. Thirty six (6/spl times/6) laser lights from a VCSEL-array module were transmitted through an image fiber with a 460-/spl mu/m diameter and consisting of 10,000 super-thin micro cores. The optical crosstalk was measured spatially and dynamically, and was less than -27 dB from dc to 3 GHz when a 1-m-long image fiber was used. We have actually transmitted bit data at a rate of 1 Gb/s, and the bit-error rate became 1/spl times/10/sup -8/ at the average received power of -27.7 dBm.

Skew evaluation using two-dimensional refractive-index profile in single-mode fiber ribbons

The skew of fiber ribbons must be small for high bit rate parallel optical transmission systems. Accurate skew evaluation using fiber parameters is important for this purpose. A simple method, based on the calculus of variations, is proposed for evaluating the skews of fiber ribbons. This method employs only one mode field (LP/sub 01/ mode) of an ideal step-index fiber as a trial function and a two-dimensional (2-D) refractive index profile. The measured skews of a 16-fiber ribbon composed of fibers with different parameters are compared with calculated values and are found to be in good agreement. The influence on the skew of several refractive index profile deviations (including asymmetric profile deviations) are evaluated using the proposed method. It is found that the asymmetric core profile has a large influence on skew whereas that of the asymmetric core-cladding boundary is relatively small.

An approach to optical parallel data transmission using optical symbolic substitution

AbstractThis paper proposes a flexible parallel optical data transmission system as follows. the data transmission itself is executed in parallel by utilizing the super‐parallelism of the light. In addition, the address information which is necessary for the transmission is super‐posed on the transmitted data. By those schemes, the capacity of the individual transmission channel as well as the number of transmission channels in the system are made variable.This paper describes first the principle of parallel optical data transmission. It is shown that the symbolic substitution (SS) is useful in the superposition and separation of the address information, which are the basic operations of the system. SS is a parallel and positioninvariant logical operation. an experimental system is constructed by the SS technique using the computer‐generated Fourier hologram (CGFH). A result of experiment is shown for the single‐channel parallel transmission of two‐dimensional data. Thus, it is shown that the flexible transmission system, where the capacity of the individual transmission channel as well as the number of transmission channels are variable, can be realized by the proposed transmission scheme.

Flip-chip planar GaInAs/InP p-i-n photodiode array for parallel optical transmission

A back-illuminated planar GaInAs/InP p-i-n photodiode array with a simple fabrication process was developed for application to parallel optical transmission. Four p-i-n photodiodes were integrated in the array. The average capacitance and dark current were as low as 0.12 pF and 8 pA, respectively, at -5 V. At a 1.55- mu m wavelength, the quantum efficiency of each photodiode was over 80%. The cutoff frequency was 8-10 GHz with four photodiodes when the bias voltage was -3 V and the load resistance was 50 Omega . Crosstalk between channels was -12 dB at the cutoff frequency and -45 dB at 1 GHz. >

Microlens array used for collimation of linear laser-diode array

A novel set of microlenses are used to collimate a set of monolithically integrated laser diodes for the purpose of parallel optical data transmission with high spatial density. The lenses were produced by melting photoresist without additional etching of the substrate. With a pitch of 250 mu m between adjacent channels an acceptable channel separation of 21 dB was achieved up to a transmission distance of 3 cm.

150 Mbits?1 ch?1 12-channel optical parallel interface using an LED and a PD array

An optical fibre parallel interface has been developed for card-cage to card-cage and board-to-board interconnections, representing a practical and promising optical interconnection. For a system design of a 12 channel, 150 Mbits−1 ch−1 optical parallel interface over a distance of 100 m, it is shown that the choice of a long wavelength LED/PD array with graded index optical fibre array meets the requirements for both power budget and skew limitation over this transmission distance. A 7 mm thick compact package transmitter and receiver module was developed, employing a Zn-doped, mesa structure, 1.3μm LED array and an isolated InGaAs PD array. An optical parallel transmission experiment over 100 m was successfully demonstrated using these modules.