Cost Analysis of PSM4 and its Application in Transceivers

What is PSM4? PSM4 is short for the 4 x 25Gbps parallel single mode technology which is proposed as a PHY solution for the 500m single mode objective. Furthermore, an update on the PSM4 transceiver relative cost analysis is provided. This update is based on PSM4 optical baseline specifications.

The following analysis indicates almost 60% cost reduction in optical transceiver is achievable with the proposed PSM4 approach, compared with the current 100GBASE-LR4, for <500m short reach SMF application.

Key factors in PSM4 technology for providing cost reduction relative to 100GBASE-LR4

Factor	Key Differentiation
Reduced Component Count	No O-MUX/DEMUX
	No TEC
	Integrated lens in LD, PD devices
	Single chip LD array, PD array
Reduced Component Cost	Spec relaxation, increased yield
	Relaxed alignment tolerances
	1-chip CMOS quad CDR with laser driver array
	Wide spectral range increases LD array yield
	Small sized OSA package w/o O-MUX/DEMUX
Reduced Assembly Cost	Relaxed tolerances enabling passive optical alignment
	Low assembly cost w/o O-MUX/DEMUX
	SMT for optical components
Reduced Test Cost	Wide spectral range eliminates wavelength test
	On-wafer laser, PD testing and burn-in

PSM4 Transmitter Optical Sub-Assembly (TOSA) cost analysis relative to 100G-LR4 and SR4

100G PMD	Fiber Type	Reach	TOSA		LDD	O-MUX	Optic Coupling	Total Rel. Cost
			LD	TEC
LR4	SMF	10km	Cooled DML	Req	SiGe	Req	Active	1
PSM4	SMF	500m	Surface Emitting DML	NR	CMOS 1-chip CDR	NR	Passive*	0.2
SR4	MMF	100m	VCSEL	NR	CMOS	NR	Passive	<0.2

PSM4 Receiver Optical Sub-Assembly (ROSA) cost analysis relative to 100G-LR4 and SR4

100G PMD	Fiber Type	Reach	TOSA	TIA	O-DEMUX	Optic Coupling	Total Rel. Cost
			PD
LR4	SMF	10km	PIN	SiGe	Req	Active	1
PSM4	SMF	500m	PIN	CMOS 1-chip CDR	NR	Passive*	0.35
SR4	MMF	100m	PIN	CMOS	NR	Passive	<0.35

PSM4 transceiver cost analysis, relative to 100GBASE-LR4 and SR4

Component	100G-LR4	100G-PSM4	100G-SR4
TOSA + LDD + O-MUX	1	0.2**	<0.2**
ROSA + TIA + O-DEMUX	1	0.35	<0.35
CDR IC	1	1	1
MISC: DC-DC, uC, Packaging	1	1	1
Assembly & Test
Total	1	0.43	<0.43

NR: Not Required
* Design Target
** Decrease including results from reduced parameter set testing.

Now an update on the PSM4 technology and relative cost analysis has been presented. Relative cost analysis indicates almost 60% optical transceiver cost reduction in a short reach 500m SMF link is achievable with the PSM4 approach, compared with the current 100GBASE-LR4.

Application of PSM4 Technology

PSM4 is generally used in the transceiver application. With this technology, optical transceivers come to have the following features.
1. Surface mount with passive alignment enables enables low cost module.
2. Use of lens-integrated optical devices reduces components and assembly costs in transceiver design.

The mainly transceiver that uses PSM4 is the 40G QSFP+. QSFP+, short for quad small form-factor pluggable plus, is designed for high-density applications. Except the 40G QSFP+ transceiver modules, FiberStore also supplies QSFP+ cables including the active optical cable (AOC), passive copper cable assembly, active copper cable assembly, and QSFP+ loopback.

The SFF-8685 document specifies a transceiver mechanical form factor with latching mechanism, host-board electrical-edge connector and cage. The hot-pluggable transceiver integrates 4 transmit and 4 receive channels. Our QSFP+ transceiver can replace up to 4 standard SFP+ transceivers. The result is greater port density and overall system cost savings over traditional Plus SFP module. Our QSFP+ cable assemblies are designed to accommodate stacked and ganged connector configurations in extremely high-density requirements. This system supports 10G Ethernet, Fibre Channel, InfiniBand, SAS and SONET/SDH standards with different data rate options.

AOCs, short for active optical cables, have extremely low power consumption of only 0.78W per cable end. This feature improves overall data center power consumption and thermal efficiency.
40G QSFP+ PSM4 AOCs use single mode silicon photonics (SiPh) to enable transmitting up to 4km on single mode ribbon fiber.

AOCs reduced cable bulk compared to larger diameter copper cabling enable deployment of additional ports for increased number of AOCs per system, resulting in more connectivity options and total system cost savings. QSFP+ loopback features a compact housing compatible with module spacing and loop optical transmit ports to receive ports for testing, burn-in and field troubleshooting.