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Submount for RF-Chokes Showing Reduced Parasitic Electromagnetic Effects

IP.com Disclosure Number: IPCOM000020133D
Original Publication Date: 2003-Oct-28
Included in the Prior Art Database: 2003-Oct-28
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Abstract

Disclosed is a submount design for discrete RF choke components used in DC bias circuits for optical transmitters. The proposed submount shows reduced parasitic electromagnetic effects. The preferred embodiment holds standard 0603 components and is attached to the surface of a silicon optical bench.

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Submount for RF-Chokes Showing Reduced Parasitic Electromagnetic Effects

Laser diodes operating in high data rate transmitters need both:

DC current supply connection (for establishing the operating point), and

wideband (AC) connection to the laser diode driver circuit (which generates the data

to be transmitted).

Especially the AC connection demands a careful design (impedance matching) over the bandwidth of the signal to be transmitted. The DC connection in itself is less sensitive but presents additional challenges for the AC design since it must be decoupled for most of the frequency range (typically beyond 100 MHz). The decoupling is usually done by discrete RF choke components which are commercially available.

In experiments it was found that parasitic electromagnetic effects associated with the RF chokes can disable the decoupling effect to such an extent that normal transmitter operation is impossible. The proposed method tries to reduce the parasitic effects by putting the discrete RF choke components on supporting submounts. The submounts have specifically designed metallic pads for electrical contact to the laser diode and the DC source.

Figure 1 shows the top view of the proposed submount which is essentially a small piece of dielectric material. Figure 2 shows a 3D view including a discrete RF choke component. The submount is designed to hold RF choke components of 0603 standard size (60 x 30 x 30 mils). Two metal pads (in yellow) are plated on the t...