Optimization of a small to‐can package electrical design for SFF/SFP optical transceiver modules

Abstract

It must be stressed that, in order to achieve a full optimization of the current integration method for a parabolic reflector, it is convenient to evaluate only the far-field samples necessary to reconstruct the antenna pattern by means of proper OSI expansions [4,6,7]. A further and very significant reduction of the computational time is thereby attainable. As a matter of fact, the few samples are needed, the direct evaluation of the ChuStratton radiation integral, shown in Eq. (1), is onerous, and the computation of the OSI formula is fast. Moreover, once these far-field samples are available, the antenna directivity can be efficiently determined by using the closed form formula proposed in [8]. In order to cope with the high demand for a drastic increase in data rates, low cost, and small-size optical transceivers in optical networks, small form-factor (SFF) small form-factor pluggable (SFP) optical transceivers have been developed [1,2]. TO-can packaging is generally considered as one of the low-cost solutions to the LD/PD chip package. In an SFF/SFP optical transceiver, the TOcan package is located at the optical front-end module. Recent trends regarding SFF/SFP transceivers indicate that the space between the transmitter and receiver section is now much narrower, such that the TO-can package size can be smaller than those of conventional transceivers. Thus, TO-46 and TO-56 were gradually replaced with TO-38, which has a smaller body size that is 3.8-mm in diameter.When the data rates of SFF/SFP optical transceivers increase, the TO-can package bandwidth as well as the LD/PD chip bandwidth become important. With increased operation frequency, the parasitic inductance and capacitance due to the physical geometries of the package increase as well. These parasitic elements tend to reduce the high-frequency gain and increase the loss, thus their impact needs to be reduced as much as possible. Thus far, we have been dependent on empirical methods for the design and manufacture of TO-can type packages and have overlooked, this aspect during the last several years. Recently, several papers have reported quantitative analyses regarding the parasitic effects [3][4][5][6]. However, in these studies less accurate 2D circuit simulation was used, and a bonding-wire model was analyzed, which may not be practical.In this paper, the geometric design of a TO-can package, focused on the optical receiver for enhanced 3-dB bandwidth performance, is investigated. We present 3D modeling, the equivalent circuit of a TO-can package, and an analysis of the parasitic elements, including inductance and capacitance. The performance evaluation of our TO-38 package is done via measurement and simulation, then we propose the optimal geometric design parameters of the package capable of achieving the higher-frequency performance. MODELINGThe geometry of the TO-38 package, included bonding-wires, PD chip, sub-mount, and leads, is illustrated in Figure 1(a). The trans-impedance amplifier (TIA) that changes the photocurrent from the PD into a...