Typical QSFP+ Connector

The QSFP+ module assembly consists of an optical ribbon fiber cable attached to the PN1000001 Si CMOS photonics chip, which is mounted on a printed circuit board (PCB) and placed within an electromagnetic interference (EMI) shielded metal housing, shown in Figure 2. The PN1000001 Si CMOS photonics chip is wire bonded directly to the PCB as shown in Figure 3.

Figure 2

PCB of QSFP+ Module Assembly

Figure 3

PN1000001 Si CMOS Photonics Die Wire bonded to the PCB Plan View

The Si CMOS photonics chip was removed from the PCB and the gel over the chip carefully removed in our lab to expose the structure of the module featuring the Si CMOS photonics die. Figure 4 and Figure 5 are tilt and cross-sectional views, respectively, of the module featuring a laser module and optical fiber assembly attached to the top surface of the PN1000001 Si CMOS photonics die. The Si CMOS photonics die is attached to a metal support.

Figure 4 

Si CMOS Photonics Die Module – Tilt View

Figure 5

Si CMOS Photonics Die module Optical Cross Section

Figure 6 is a detailed cross-sectional SEM image showing the coupling between the optical fiber and Si CMOS chip. The fiber assembly is epoxied to the top of the Si CMOS chip such that each fiber is centered over a grating coupler. The fiber core is located in the middle of the fiber cladding and is not visible in this cross-sectional image.

Figure 6

Optical Fiber to Si Chip Coupling SEM Cross Section

Figure 7 and Figure 8 show plan and side-view X-ray images, respectively, of the laser module attached to the PN1000001 Si CMOS photonics die. The laser module is similar to laser modules used in typical fiber-to-home applications, but modified to bounce the light originating from the side of the laser die into the Si photonics chip. The laser module consists of a laser die, ball lens, and isolator, all aligned and positioned over a micro-machined Si optical bench and covered with a Si cap that is etched to form a cavity over the laser module elements. The underside part of the cap is coated with a reflector, which bounces light from the laser into the Si photonics die.

Figure 7

Laser module – plan-view X-ray

Figure 8

Laser module – side-view X-ray

A die photograph of the PN1000001 Si CMOS photonics die extracted from the module is shown in Figure 9. The transceiver die uses four transmit (TX) and four receive (RX) channels, a digital core, and eight fiber array I/Os. The die also features a channel transmit section in the lower half of the die and a four-channel receive section in the upper half of the die.

Figure 9