#cfp modules

As a new emerging technology, 100G is some sort of evolution and part of revolution. The new CFP (C form-factor pluggable) optics is now a revolutionary step as one form factor of 100G optic transceiver. The CFP modules offer the enabling step for cost-effective and successful 100G deployment. So what is it? And how does it work in 100G network? This article would give a comprehensive introduction to CFP modules.

CFP Wiki

Abbreviated as CFP transceiver, C Form-Factor Pluggable transceiver is a multi-sourced pluggable transceiver used in the transmission of high-speed digital signals. It is specified by a multi-source agreement (MSA) between competing manufacturers. The c stands for the Latin letter C used to express the number 100 (centum), since the standard was primarily developed for 100 Gigabit Ethernet systems. It is a hot-swappable input/output transceiver that is used in the data communication and telecommunication networks.

The CFP transceiver was designed after the small form-factor pluggable transceiver (SFP) interface, but is significantly larger to support 100 Gbit/s. While the electrical connection of a CFP transceiver uses 10 x 10 Gbit/s lanes in each direction (RX, TX) the optical connection can support both 10 x 10 Gbit/s and 4 x 25 Gbit/s variants of 100 Gbit/s interconnects (typically referred to as 100GBASE-SR10 in 100 meter MMF, 100GBASE-LR10 and 100GBASE-LR4 in 10 km SMF reach, and 100GBASE-ER10 and 100GBASE-ER4 in 40 km SMF reach respectively.)

Core Features of CFP Modules

- Support to 103 Gbps and 112 Gbps aggregate bit rates.

- Connector Interface

- Operating Case Temperature

- Diagnostic Monitoring

- RoHS6 Compliant

- Single 3.3V Supply for Power and a Power dissipation < 12W

One distinctive feature of CFP modules is that they support digital diagnostic monitoring functions or the digital optical monitoring. This is the feature that gives users the ability to monitor the real-time parameters such as the optical output power, the optical input power, the temperature, the laser bias current and the transceiver supply voltage.

Inner Structure of CFP Modules

The basic CFP modules consist of the following parts.

1. An Integrated Coherent Optics Transmitter which sends the TX optical signal.

2. An Integrated Coherent Optics Receiver which receives the RX optical signals.

3. The CFP connector

4. Coherent DSP

Most of the CFP optical transceivers adhere OIF CFP-ACO (Analog Coherent Signals) and are connectable to multiple DSP's. The biggest engineering challenge that CFP2 faces is the adoption of the high-speed 25 Gbps electrical interface due to the reason that the CFP was based on the third generation.

It can be a multimode parallel optic transceiver module that is designed to offer high-density 100G Ethernet and Optical Transport Network (OTN). The device is designed to offer maximization of the delivery of the 10G data channels for the 100G networks that support 100 Gbps SR10 and 10 X 10 Gbps.

Development of CFP Modules

The original CFP specification was proposed at a time when 10 Gbit/s signals were far more achievable than 25 Gbit/s signals. As such to achieve 100 Gbit/s line rate, the most affordable solution was based on 10 lanes of 10 Gbit/s. However, as expected, improvements in technology has allowed higher performance and higher density. Hence the development of the CFP2 and CFP4 specifications. While electrical similar, they specify a form-factor of 1/2 and 1/4 respectively in size of the original specification. Note that CFP, CFP2 and CFP4 optical transceiver are not interchangeable (but would be inter-operable at the optical interface with appropriate connectors). The following table shows the basic parameter of CFP, CFP2 and CFP4 transceivers.

Conclusion

With the explosive growth in mobile data traffic, data centers, and cloud services, people’s call for 100G Ethernet is more higher than ever before. To build and support the 100G Ethernet, a variety of technologies and devices are needed. 100G CFP modules, QSFP28 modules and 100G CFP to QSFP28 adapter converter module are of necessity. This article would put emphasis on introducing four 100G CFP to QSFP28 adapter converter modules and their applications.

Overview on 100G CFP to QSFP28 Converter Module

The 100G CFP to QSFP28 adapter converter module is a high performance, hot pluggable, and interconnect solution supporting 100G Ethernet and Telecom. The converter module converts a CFP MSA interface to 1-port of 100GE QSFP28. It is compliant with the CFP MSA. The converter module supports FEC (Forward Error Correction) function; the user can enable the FEC function through the register configuration.

100G CFP to QSFP28 Converter Module

100G CFP to QSFP28 adapter converter module converts 10 bidirectional 10G channels to 4 bidirectional 25G channels operating at up to 28Gbps per channel. By plugging 100G QSFP28 transceiver into the QSFP28 connector on the 100G CFP to QSFP28 adapter converter module, CFP module and QSFP28 module are interconnected. The 100G CFP to QSFP28 converter module datasheet is shown as below:

Cisco 100G CFP to QSFP28 Converter Module

Cisco CVR-CFP-100G supports modules with a 4x25G electrical interface. The CVR-CFP-100G supports modules with a 10x10G electrical interface such as 100G CFP. The CVR-CFP-100G CFP to QSFP28 converter module supports the two aggregate data rates of 100Gbps Ethernet and Optical Transport Network (OTN) rates. The CVR-CFP-100G CFP to QSFP28 converter module supports only the 100GBase Ethernet data rate. The Cisco CVR-CFP-100G CFP to QSFP28 converter module datasheet is shown as below:

100G CFP2 to QSFP28 Converter Module

Like being mentioned 100G CFP to QSFP28 adapter converter module, 100G CFP2 to QSFP28 converter module converts 10 bidirectional 10G channels to 4 bidirectional 25G channels operating at up to 28Gbps per channel. By plugging 100G QSFP28 transceiver into the QSFP28 connector on the 100G CFP2 to QSFP28 adapter converter module, 100G QSFP28 transceiver is in the CFP2 port of your device. In this way, power consumes less than using an equivalent CFP2. The 100G CFP2 to QSFP28 converter module datasheet is shown as below:

Cisco 100G CFP2 to QSFP28 Converter Module

The Cisco CVR-CFP2-100G adapter converter module allows a Cisco 100G QSFP28 transceiver module to be plugged into a CFP2 port and to emulate an optical CFP2 100G Module. The Cisco CVR-CFP2-100G CFP2 to QSFP28 converter module datasheet is shown as below:

Conclusion

Although 10/40G Ethernet nowadays still captures the major position in the world of telecommunication, service providers and enterprise data centers are actually undertaking an infrastructures transformation. Which fuels the demand for higher speeds and better performance 100G transceiver, making migration to 100G an inevitable trend. Optical transceiver modules always pertain to an integral part of overall system design, as for 100G CFP modules, the options vary widely. This article makes a comparison between the most common two CFP transceivers: 100G SR10 and 100G LR4 CFP modules.

Basics of 100G CFP Modules

CFP transceiver is a hot pluggable form factor designed for optical networking applications. CFP is the acronym of 100G (here C equals 100 in Roman numerals) form factor pluggable. The name clearly indicates that CFP modules are designed typically for 100G interfaces. To make it easier, let’s begin with general CFP modules architecture. It basically consists of two parts—electrical interface interacting with equipment, and line card interface and optical line interface. The following figure displays the general architecture of 100GBASE CFP transceiver.

From equipment line card to electrical interface, CFP transceiver has several “M-Lines” with 10Gbps speed. If CFP modules are working 100GBase-LR4 mode, then it has 10 x 10Gbps M-Lines. As for 40GBase-LR4, it uses 4 x 10Gbps M-Lines. The so called “gear box” is electrical 10:4 mux/demux module aggregating up to 10 M-Line interfaces in maximum 4 N-Line interfaces. Each N-Line is 25Gbps for 100GBase-LR4 and 10Gbps for 40GBase-LR4. The N-Line is converted to optical signal with different wavelength and all four wavelengths are transmitted to CFP transceiver line interface using built in passive optical multiplexers.

100G SR10 and 100G LR4 CFP Modules Overview

100G CFP modules offer connectivity options for a wide range of service provider transport, data center networking, and enterprise core aggregation applications. The basic information of CFP-100G-SR10 and CFP-100G-LR4 module is provided below.

100G SR10 CFP Modules

CFP-100G-SR10 is an IEEE standardized CFP transceiver supporting link lengths of 100 m and 150 m respectively on laser-optimized OM3 and OM4 multifiber cables. It primarily enables high-bandwidth 100-gigabit links over 24-fiber ribbon cables terminated with MPO/MTP-24 connectors. It can also be used in 10 x 10 Gigabit Ethernet mode along with ribbon to duplex fiber breakout cables for connectivity to ten 10GBASE-SR optical interfaces. 100G SR10 CFP interface serves as a more cost-effective solution, which is optimized for data center application but limited to short distances.

100G LR4 CFP Modules

CFP-100G-LR4 is standardized by IEEE using standard LC dual fiber interface with single-mode cable, but running four optical wavelengths each direction (1295.56 nm, 1300.05 nm,1304.59 nm, 1309.14 nm) and muxing/demuxing of these wavelengths happening inside CFP module. Each wavelength is running at 25.78 Gbps and it is possible to achieve up to 10 km. Compared to 100G SR10 CFP, 100G LR4 CFP delivers much better reach for long-haul applications, but at a cost premium.

Comparison Between 100G SR10 and 100G LR4 CFP Modules

In this section, we’re trying to figure out the difference between CFP-100G-SR10 and CFP-100G-LR4 from the perspective of connectors and cabling used on each. For connectors, 24-fiber MPO/MTP connector is for 100GBASE-SR10 CFP transceiver while dual SC/PC connector for 100GBASE-LR4. Note that only patch cords with PC or UPC connectors are supported. The cabling specification and features for 100G SR10 and 100G LR4 CFP modules are presented in the following diagrams.

Conclusion

The rapid development in telecom industry is driving massive demand for higher bandwidth and faster data rate, from 10G to 40G and 100G, will this keep going on? The answer is definitely “Yes”. Some time ago, migration from 10G to 40G or 25G to 100G has been a hot spot among data center managers. While recently, 400G solutions and 400G components are coming. Are you ready for 400G? This article will share some information about 400G Ethernet.

Overview of 400G

In the past couple of years, modules with four 25/28G lanes or wavelengths are the solutions for 100G Ethernet. However, they were expensive at the beginning. Until 2016, the optical components industry has responded to the demands with 100G solutions that already cost less per gigabit than equivalent 10G and 40G solutions, and new developments to further drive down cost and increase bandwidths. The next generation is 400G Ethernet. The IEEE has agreed on PSM4 with four parallel fibers for the 500 meters 400GBASE-DR4 specification that is part of the IEEE802.3bs standard being developed for approval by the end of 2017. The industry is already developing optical components for 400G Ethernet solutions. The following figure shows telecom and datacom adoption timelines.

We can visually see that telecom/enterprise applications first adopted 100G technology in the form of CFP modules. Data centers generally did not adopt 100G interfaces until the technology matured and evolved towards denser, lower power interfaces, particularly in the form of QSFP28 modules. However, as the hyperscale data center market scales to keep pace with machine-to-machine communications needs, data center operators have become the first to demand transmission modules for data rates of 400G and beyond. Therefore, the 400G era is now upon us.

Modules for 400G

We know that the QSFP28 modules for 100G Ethernet and SFP28 modules for 25G Ethernet are now the dominant form factors. Though CFP, CFP2 and CFP4 modules remain important for some applications, they have been eclipsed by QSFP28 modules. To support higher bandwidth, what is the right module for 400G? The first CFP8 modules are already available. QSFP-DD is backward compatible with QSFP, and OSFP may deliver better performance, especially as networks move to 800G interfaces.

CFP8 module: CFP8 module is the newest form factor under development by members of the CFP multisource agreement (MSA). It is approximately the size of CFP2 module. As for bandwidth density, it respectively supports eight times and four times the bandwidth density of CFP and CFP2 module. The interface of CFP8 module has been generally specified to allow for 16 x 25 Gb/s and 8 x 50 Gb/s mode.

QSFP-DD module: QSFP-DD refers to Quad Small Form Factor Pluggable Double Density. It uses eight 25G lanes via NRZ modulation or eight 50G lanes via PAM4 modulation, which can support optical link of 200 Gbps or 400 Gbps aggregate. In addition, QSFP-DD module can enable up to 14.4 Tbps aggregate bandwidth in a single switch slot. As it is backwards compatible with QSFP modules, QSFP-DD provides flexibility for end users and system designers.

OSFP module: OSFP (Octal Small Form Factor Pluggable) with eight high speed electrical lanes is able to support 400G (8x50G). It is slightly wider and deeper than the QSFP but it still supports 36 OSFP ports per 1U front panel, enabling 14.4 Tbps per 1U. The OSFP is able to meet the projected thermal requirements for 800 Gbps optics when those systems and optics become available in the future.

Conclusion

Judging from the current trends, 400G will become the mainstream in the near future. But there are still some challenges for it to overcome, such as high capacity density, low power consumption, ever lower cost per bit, and reliable large-scale manufacturing capabilities. You never know what surprise the network will bring to you, let’s wait and see the 400G’s time.

400 Gigabit Ethernet was planned to be released in December this year. It is designed to meet IEEE P802.3bs Task Force standard and to apply to both metro and long-haul networks. The 400GbE operates over 100 m of multimode fiber, 500 m of singlemode fiber, 2 km of SMF, and 10 km of SMF. 400G CDFP and CFP8 are two form factors of 400G Ethernet technology. This article would give a introduction to 400G CDFP and CFP8 modules and make a comparison between them.

Introduction to 400G CDFP Module

The CDFP is short for 400 (CD in Roman numerals) Form factor Pluggable, which is designed to provide a low cost, high density 400 Gigabit Ethernet solution. It features as front panel, hot-pluggable, 16 channel and 400 Gbps module. CDFP will be a short reach module, which enables 4 Terabit line cards. From the perspective of interface, it is very similar to the QSFP and CXP modules. CDFP developers have targeted using the developing IEEE802.3bs specification for Ethernet 400GBaseSR, 400GBaseLR.

5 meter direct attach cables

100 meter multimode fiber

500 meter parallel singlemode fiber

2 kilometers of duplex singlemode fiber

Figure2: 400G CDFP Module

Information About 400G CFP8 Module

Following CFP2 and CFP4 naming, CFP8 module was proposed in the year 2015. CFP8 is a new form factor which is still under development by members of the CFP multisource agreement (MSA). The form factor of CFP8 is amounting to CFP2, but it supports 4 × 100G and 400G, for example, 4×CFP2’s 1×100G. The CFP8 uses a new 16 × 25G electrical I/O connector. The CFP8’s interface has been generally specified to allow for 16 × 25 Gb/s and 8 × 50 Gb/s mode. From the point of bandwidth density, the CFP8 module is eight times larger than the CFP module and four times larger than the CFP2 module.

Figure3: 400G CFP8 module operation

Example IEEE specifications supported by CFP8:

400GBASE-SR16 parallel MMF (16x25G NRZ)

400GBASE-FR8/LR8 duplex SMF (8x50G PAM4 WDM)

400GBASE-DR4 parallel SMF (4x100G PAM4)

CDAUI-16, CDAUI-8

Figure4: Form factors of CFP modules

Among all the specifications on the above, 400GBaseDR4 is the most revolutionary one. 400GBaseDR4 uses 4x100G parallel SMF PAM4 signaling technology. This technology is also aimed at fitting in the CFP4 21.5-mm width module size, while using 12 (SMF) fibers within a 1×12 MPO optical connector and the host board electrical 56-pin edge connector.

Low power consumption is also a distinctive feature of CFP8. Active optical modules have been widely deployed in the process of data transmission, but some of them or some copper applications really cost a lot and consumes much power. CFP8 module uses internal mid-board optical or electrical interconnect flyovers and bulkhead MPO or MXC connectors to connect the switch. This reduces power consumption to a great extent.

400G CFDP Vs. CFP8

—Form factor

CDFP was proposed earlier than CFP8, it has larger form factor than CFP8.

—Supported fiber type

CDFP supports passive and active copper cable, active optical cable and multimode fiber while CFP8 supports singlemode and multimode fiber.

—Transmission distance

CFP8 modules support longer data link distance compared with CDFP modules.

—Applications

The CDFP modules provide a very versatile solution for data center interconnects. CFP8 would be used in high-density 4x100GbE fan-out applications, such as datacom applications or in ITU-T for telecom applications.

Conclusion