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200G QSFP56 Technology - Overview
With the ever-increasing demands of optical communication and interconnection networking, the transmission rates and technological advances of optical transceivers continues unabated.
Whilst 100G technology has become the mainstream, increased bandwidth, port density and energy consumption requirements are driving the transition to 200G, 400G, 800G and beyond.
While 400G & 800G technology remains largely the domain of the Original Equipment Manufacturers (OEMs), Approved Technology are seeing increasing demand for our more cost-effective compatible transceivers in the 100G and 200G space.
This article shines the spotlight on 200G QSFP Technology with an explanation of the different types of technology available.
200G QSFP56 and 200G QSFP-DD Technology
There are 2 types of QSFP 200G technology, QSFP56 and QSFP-DD
The 200G QSFP56 form factor is an evolution of 40G QSFP+ and 100G QSFP28, designed for 40G, 100G and 200G ethernet respectively. This form factors support 4 channels, significantly increasing the port-density by 4x compared to the SFP+ form factor
To clarify, there is no difference between the terms “QSFP56”, “QSFP200” and “200G QSFP” They all refer to the same transceiver type. The electrical data path interface of a 200G QSFP consists of 4 lanes, with each lane carrying 50Gbps of data when configured for 200G operation. Each lane of a 200G QSFP is designed to handle up to 56Gbps, hence it is often referred to as a QSFP56.
The 200G QSFP-DD (Quad Small Form Factor Pluggable Double-Density) optical transceiver is compliant with IEEE802.3bs and QSFP-DD MSA standards. “Double Density” means that the module supports double the number of high-speed electrical interfaces compared to the standard QSFP28 module. The QSFP-DD package comes with an 8-channel electrical interface, while the QSF56 has a 4-channel electrical interface.
QSFP Form Factor Channels
QSFP+: 40GBase - 4 x 10Gbps channels in a QSFP form factor
QSFP28: 100GBase - 4 x 25 to 28Gbps channels in a QSFP form factor
QSFP56: 200GBase - 4 x 50 to 56Gbps channels in a QSFP form factor
QSFP-DD: 200GBase - 8 x 25Gbps channels in a QSFP-DD form factor
QSFP 200G Transceivers modules available from Approved Technology
Most commonly used 200G QSFP56 & QSFP-DD Technologies
200G QSFP56 SR4
QSFP-200G-SR4 is full-duplex with 4 independent transmit and receive channels, each capable of 53.125Gbps operation for an aggregate data rate of 200Gbps on 70 meters of OM3 multi-mode fibre. The central wavelengths of all 4 parallel lanes are 850nm. It contains an optical MPO-12 APC connector for the optical interface and a 38-pin connector for the electrical interface.
200G QSFP56 FR4
QSFP-200G-FR4 converts the 4-channel 200Gbps PAM4 (Pulse Amplitude Modulation 4) electrical input data into CWDM (course wavelength division multiplexing) optical signals by 4-wavelength EMLs (Electro-Absorption Lasers). The central wavelengths of the 4 CWDM channels are 1271, 1291, 1311, and 1331nm as members of the CWDM wavelength grid defined in ITU-T G.694.2. It contains a duplex LC connector for the optical interface and a 38-pin connector for the electrical interface. It is designed for 2km optical communication applications.
200G QSFP-DD LR4
200G QSFP-DD LR4 converts the 8-channel of 25Gbps or 4-channel of 50Gbps electrical input data into LWDM (LAN Wavelength Division Multiplexing) optical signals. It contains a duplex LC connector for the optical interface and a 76-pin connector for the electrical interface. This transceiver operates with SMF (single-mode fibre) which minimises the optical dispersion in the long-range environment. Host FEC (Forward error correction) is used to support up to 10km of fibre transmission.
200G QSFP-DD ER4
200G QSFP-DD ER4 incorporates 4 independent channels on LWDM4 (LAN Wavelength Division Multiplexing – 4 Channels) 1295.56, 1300.05, 1304.58, and 1309.14nm centre wavelength, operating at 50Gbps per channel. It contains a duplex LC connector for the optical interface and a 76-pin connector for the electrical interface. This transceiver operates with SMF (single-mode fibre) which minimises the optical dispersion in the long-range environment. Host FEC (Forward error correction) is used to support up to 30km of fibre transmission and built-in PFEC for 40km transmission.
Upgrading from 100G to 200G – Optical fibre connections
The existing cabling can be used when upgrading to 200G from 100G if the current 100G links use either of the below types of fibre connection:
- Duplex SMF with a maximum length of 2km - QSFP-200G-FR4 technology uses the same fibre type and connectors (duplex LC, SMF) as 100G-CWDM4, 100G-LR4, 100G-LRL4, 100G-DR, 100G-FR and 100G-LR.
- Parallel MMF with a maximum length of 70m for OM3, or 100m for OM4. QSFP-200G-SR4 uses the same fibre type and connectors (MPO-12, parallel MMF) as 100G-SR4, 100G-XSR4.
Dual rate 200G QSFP transceivers and direct attach can operate at 100G provided that the QSFP200 switch port that contains the transceiver is configured for 100G.
There is no industry standard for 200G over duplex MMF. QSFP200G-SR4 uses parallel multimode optical fibre using an MPO-12 optical connector. This is the same fibre type and fibre connector as used for QSFP100G-SR4.
The benefits of migrating from 100G to 200G technology
Increased bandwidth needs can be met with a lower cost and power per gigabit by doubling bandwidth density.
Ability to upgrade transceivers with no requirement to change the existing fibre cabling.
The opportunity to halve the number of patch panels, connectors and fibre links when migrating from 100 to 200G
The difference between NRZ and PAM4 optical modulation
NRZ stands for “Non-Return to Zero” modulation. It is an electrical or optical data channel where only two amplitude levels (or symbols) are allowed. One amplitude level represents a digital ‘1’ and the other level represents a digital ‘0’.
NRZ is the simplest way to transmit digital data and has been the predominant modulation method for transmitting data up to 25Gbps.
PAM-4 stands for Pulse Amplitude Modulation 4. ‘4’ refers to the number of different amplitude levels (or symbols) of the electrical or optical signal carrying the digital data. Each symbol cycle can represent 2 bits of logical information (0, 1, 2, 3), that is, four levels in one time unit, twice as many bits as a NRZ waveform at the same symbol rate. This leads to greater transmission efficiency and lower Bit Error Rate (BER).
All 200G QSFP modules utilise 4x electrical lanes in each direction (4 transmit lanes and 4 receive lanes), operating at a data rate of 50Gb/s PAM-4, enabling an aggregate bandwidth of 200Gbps. Dual rate 200G QSFPs allow the electrical interface to be configured to operate at 4x 25Gbps NRZ, for an aggregate bandwidth of 100Gbps.
Unlike NRZ, 4x50Gbps PAM4 technology for 200G transmission does not require the use of eight 25G channels for 200G transmission, which saves fibre cost and reduces link loss.
Breakout scenarios
Optical breakouts allow one QSFP200 port to break out and connect to multiple separate ports of lower data rates. Here is just one example below.
Optical transceiver technology continues to evolve and 200G technology will soon become the new mainstream preference in compatible transceivers for interconnection networking to support high-speed data transmissions.
ATGBICS is committed to being your trusted partner and supporting you with our compatible solution. Our products meet all MSA standards and protocols and risk-free with our Lifetime Replacement Warranty. Our controlled BOM management guarantees compatibility, traceability, and accuracy. Each product is uniquely serialised with date codes no longer than 120 days. Contact us today with your requirements or check out our optical transceiver product range.
