Vertical-cavity surface-emitting lasers and smart pixels for optical interconnection systems
Though TDM (and recently WDM) are generally adopted to increase the total throughput in optical communication systems, SDM must be more effective in most optical interconnection systems. This is because SDM has more advantage in cost and power consumption than TDM, when the transmission distance is rather short, i.e. less than a few hundred meters. VCSEL and smart pixel arrays are very important for constructing optical interconnection systems because they can emit, switch and process a number of broadband optical signals simultaneously. This paper reviews VCSELs and VCSEL-based smart pixels, and discusses the issues for their application to optical interconnections. VCSELs and smart pixels are applicable to three types of parallel optical interconnections: 1) parallel optical fiber link-the optical signals from the SEL array are transmitted through a fiber ribbon for distances less than a few hundred meters; 2) free-space optical interconnects-high-density optical signals from a two-dimensional SEL array are distributed into several ports for distance shorter than one meter; 3) reconfigurable optical interconnects nterconnect patterns among processors are changed dynamically by means of free-space photonic switching networks.
Multimode WDM optical data links with monolithically integrated multiple-channel VCSEL and photodetector arrays
We report on the design and implementation of a novel multiple-wavelength optical data link for low-cost multimode wavelength-division multiplexing (WDM) local-area network applications. This link utilizes a monolithically integrated multiple-wavelength vertical-cavity laser array and a narrow-band resonant-cavity photodetector array to transmit multiple channels of information simultaneously via a single multimode fiber. A detailed analysis on wavelength tuning and threshold characteristics of different laser cavity designs is presented. Theoretical results are compared to our experimental data. On the receiver part, both Schottky and p-i-n photodetectors with a single- or coupled-cavity structure are discussed. A novel p-i-n resonant-cavity photodetector design with a partially oxidized front mirror for linewidth control is proposed. Moreover, we also demonstrate preliminary measurements on the optical link built with our multiple-wavelength vertical-cavity laser array and photodetector array. Finally, the feasibility of constructing a multiwavelength optical data link with a single dual-core multimode fiber and an integrated laser/detector array is evaluated.
Avocado Flowering 1
The avocado (Persea americana Mill.) has increased in importance over the years in many countries around the world. The United States, Mexico and Brazil lead in world commercial production, while Israel, South Africa, Australia, New Zealand, the Philippines, Spain, Cyprus, Canary Islands, Chile, Ecuador, Venezuela, Greece, and the Caribbean area are actively increasing commercial production (B.O. Bergh, personal communication; Gustafson 1976). The history of the avocado has been detailed by Gustafson (1973, 1975,1976) and others (Bergh 1975b, Knight 1980; Popenoe 1924; Ruehle 1958; Schroeder 1958; Williams 1976). Several reviews have been published on various aspects of the avocado, including its botany (Knight 1980; Purseglove 1968; Williams 1976), breeding (Bergh 1975b), horticulture (Hodgson 1930b; Ruehle 1958; Ryerson et al. 1924), cultivars (Campbell and Malo 1976), and pollination (Gustafson and Bergh 1966). A recent collection of papers discussing the horticultural aspects of avocado production is found in Sauls et al. (1976).