Demystifying Transceiver Part Numbers Part 2: Unique data rates

Welcome to Part 2 of our series on demystifying transceiver part numbers. In the first part, we looked at common form factor types and how we provide information about them in a three-part format that looks something like: XXX-XXXXX-XXX. We covered form factors from our PRE-SFP code to our PRE-OSFP800 offerings. In this second part, we look at different variants of data rates we can encounter in our transceiver part number nomenclature: multi-rate, dual-rate, Fiber Channel and CPRI/eCPRI. Let’s dive in!

Multi-Rate Transceivers

Multi-rate transceivers are optics that can be toggled back and forth between different encapsulation methods from the host side. Common rate specifications include:

• 1GbE / OTN OTU1/OC-48
• 10GbE / OTN OTU2/2e
• 40GbE / OTN OTU3
• 100GbE / OTN OTU4

As the above pairings show, a multi-rate 10G optic, for example, can operate at either 10G Ethernet or up to one of the Optical Transport Network (OTN) data rates. In the example of this pairing, there’s a distinction between standard Ethernet data rates and the Optical Transport Unit (OTU) data rates specified in the ITU-T G.709 standard. Here, 10GbE refers to a standard Ethernet transmission rate of 10 Gbps. A transceiver capable of transmitting OTU2e rates will transmit up to 11.1Gbps, which is higher than its Ethernet counterpart because it includes additional overhead used to encapsulate the original data as it travels through the OTN.

Multi-rate transceivers are used widely in the telco industry by service providers (MSOs, MNOs, etc.) in need of efficient transport of traffic across long-haul OTNs. Because multi-rate optics offer compatibility across different encapsulation methods, standards and data rates, they enable network operators to use the same equipment for different types of services, thus avoiding the need to make constant hardware upgrades to support evolving network requirements. In other words, multi-rate optics enhance operator scalability.

From a naming perspective here at Precision OT, we simply add an M at the end of the second stanza in our standard three-part naming format that looks like: XXX-XXXXXX-XXX. For example, an SFP10G optic featuring multi-rate capabilities is named as PRE-SFP10GM, where the “M” denotes multi-rate.

Dual-Rate Transceivers

Dual-rate transceivers are optics that can have their data rate toggled back and forth between common Ethernet data rates such as 1GbE and 10GbE by the host device. Common pairings exist as follows:

• 1GbE/10GbE
• 10GbE/25GbE
• 40GbE/100GbE

These transceivers are designed to provide network operators with flexibility and cost efficiency for network upgrades and management. For example, a network operator with a 1GbE network that has plans to eventually scale up to 10GbE speeds once the rest of the network is ready can leverage a 1GbE/10GbE dual rate optic now to ensure a smooth transition later to the higher data rate. In this way, dual-rate optics enable enterprise data center operators, telcos (MSOs/MNOs) and internet and cloud service providers to balance meeting ever-increasing bandwidth demands with a financial landscape of compressed budgets. It is important to note that the toggling between data rates will need to be enabled by the host, and thus, dual-rate optics compatibility is very much host and host SW dependent.

Because dual-rate transceivers focus on bridging the gap between two performance tiers, they are especially useful for networks in the process of transitioning from one data rate to another but still need to maintain backward compatibility. For data center networks, dual-rate optics are especially handy. For example, a 10GbE/25GbE dual-rate transceiver enables data center network engineers to shift up to 25GbE Ethernet for better performance and efficiency yet still interact with legacy 10Gbe equipment. From an MNO perspective, dual-rate optics also provide excellent future-proofing capabilities, allowing them to, in the case of 5G fronthaul networks, implement 25GbE speeds easily down the line as user demand (and correlated data traffic) increases. 

Like the multi-rate optic naming convention, we denote an optic’s dual-rate capabilities here at Precision OT by adding a “D” to the end of the second stanza: PRE-xxxxxxD. Thus, in the case of an SFP10G transceiver, the name would feature as PRE-SFP10GD for dual rate.

Fiber Channel Optics

Fiber Channel (FC) optics play a vital role in storage area networks (SANs) by enabling high-speed data transfer between servers and storage devices. These transceivers are designed to handle FC protocols optimized for reliable, low-latency communication and large data transfers.

Precision OT offers FC optics at a variety of data rates, including 4G, 8G, 16G, 32G and 64G. We denote FC optics simply by putting the data rate in the second stanza in the format PRE-SFPxxG. Therefore, a 32G fiber channel optic would be denoted as PRE-SFP32G, while a 4G FC optic would be denoted as PRE-SFP4G. Additional information about these transceivers, such as distance covered or temperature rating, would be incorporated into the third stanza. For example, PRE-SFP4G-5(I), denotes a 4G FC optic with a transmission distance of 5km with I-Temp available. We will look at this type of additional information in the following sections.

CPRI/eCPRI

CPRI (Common Public Radio Interface) and eCPRI (enhanced CPRI) transceivers are optical modules critical in 4G and 5G network deployments. These optics connect remote radio units (RRUs) with baseband units (BBUs). CPRI defines 10 unique line rates (Line Rate 1 through Line Rate 10), each corresponding to specific data transmission speeds. They are as follows:

• Line Rate 1: 614.4 Mbps
• Line Rate 2: 1.2288 Gbps
• Line Rate 3: 2.4576 Gbps
• Line Rate 4: 3.072 Gbps
• Line Rate 5: 4.9152 Gbps
• Line Rate 6: 6.144 Gbps
• Line Rate 7: 9.8304 Gbps
• Line Rate 8: 10.1376 Gbps
• Line Rate 9: 12.1651 Gbps
• Line Rate 10: 24.3302 Gbps

Yet as the industry evolved towards widespread adoption of 5G, a solution to CPRI’s inefficiencies became necessary. CPRI’s need for a dedicated link for each antenna and continuous bitstream method makes it difficult to scale upwards to support 5G’s massive Multiple Input Multiple Output (MIMO) technology. That’s where eCPRI comes in. By leveraging a packet-based, ethernet-friendly approach, eCPRI is 10 times more efficient than CPRI and can support the 25G speeds (and beyond) necessary for 5G deployments. In other words, it offers network operators more flexibility in scaling to meet the demands of 5G.

From a naming perspective, a transceiver compatible with CPRI Line Rate 7 (9.8304Gbps) will be labelled as PRE-SFP10G-10I-CP07, where CP07 refers to the supported line rate. Importantly, the I after 10 stands for I-temp, which is a subject that we will cover in part 3 of our series. Whenever transceivers go into outdoor environments, such as radios in 5G deployments, temperature ratings become a critical consideration.

For questions about transceiver choices, contact our team of engineers.