How thin transponders help you get more from coherent pluggables

In life, we sometimes face choices where neither option is perfect and both require trade-offs. Imagine you're choosing between two cars: one is a fuel-efficient compact car with excellent mileage but low horsepower, and the other is a powerful sports car that delivers thrilling performance but consumes far more fuel. The dilemma lies in balancing practicality with passion. But what if you had a third choice, a car that combines good horsepower and decent fuel consumption? 

Network operators no longer have to choose between embedded transponders and Coherent Routing, also known as IP over DWDM (IPoDWDM), when it comes to deployment models for coherent pluggables. There’s now a compelling third option: thin transponders.

Why consider thin transponders?

In a prior blog, we discussed how thin transponders provide a new deployment model by leveraging the latest generation of pluggable coherent technology. They combine some of the strengths of embedded transponders and Coherent Routing without the related disadvantages. 

Just like embedded transponders, thin transponders offer multiple client ports (100G, 200G, 400G or 800G) for gray optics to carry traffic from other platforms such as routers, along with multiple line ports for high-capacity coherent pluggables such as 400G ZR, 400G ZR+, 800G ZR or 800G ZR+. 

Similar to IPoDWDM solutions, thin transponders offer lower CAPEX, lower power consumption and a smaller footprint, but without operational challenges. They also combine some of the advantages of embedded transponders, such as multiple client-side aggregation, operational domain separation and some of the optical capabilities of full-fledged embedded transponders.

Thin transponders also enable “technology lifecycle separation” between the photonic and the IP layer, which allows network operators to benefit from the latest generation of coherent pluggables, such as ICE-X 800G ZR/ZR+, in existing 400G routers. This helps them maximize return on investment (ROI) and operational flexibility by avoiding a network-wide upgrade to the latest 800G-capable generation of all routers.

While thin transponders enable compelling reductions in power consumption and footprint, embedded transponders remain the best choice for improving spectral efficiency and maximizing fiber capacity. For example, embedded transponders deliver on average 20% more fiber capacity than pluggable-based thin transponders for the same optical link. 

Comparing DSP use by embedded and thin transponders

The primary difference between embedded and pluggable solutions lies in the digital signal processor (DSP). With more space and power to work with, the DSP for embedded solutions can be physically larger, support more gates and enable more functionality. This includes a full suite of advanced features, such as support for a wide range of modulation formats and very high chromatic dispersion compensation, which enables networks to extract maximum capacity per fiber. 

In contrast, when packaged inside a compact coherent pluggable, such as 800G QSFP-DD or OSFP, the same DSPs must operate within stringent space and thermal constraints, which limits the set of capabilities that can be supported. Even so, coherent pluggables still deliver significant advantages by reducing space and power consumption compared to traditional systems. And while they cannot match the full performance and feature set of full-fledged embedded optical engines, the latest generation based on 3 nm technology can still comfortably reach long-haul distances, as highlighted in Table 1.

Table 1: Comparison of 3nm DSPs in embedded transponders and in 800G coherent pluggables

Use cases for thin transponders

As noted, thin transponders combine key attributes of embedded transponders and Coherent Routing, providing cost-effective, flexible and highly reliable optical transport that leverages the latest generation of coherent pluggables. Thin transponders are the solution of choice when space and power are limited, and a low variety of client services is required. They also reduce sparing costs because the same 800G coherent pluggables can be used in Coherent Routing/IPoDWDM applications and thin transponder modules. Figure 1 depicts a typical thin transponder application: connecting data centers.

Figure 1: Using a thin transponder to connect data centers 

Another key application of thin transponders is backhauling data center traffic at submarine landing terminal equipment (SLTE) sites. Embedded transponders are used to maximize fiber capacity from the wet plant. Thin transponders are used to reduce power consumption and footprint for traffic in the dry plant, connecting inland data centers as depicted in Figure 2.

Figure 2: Data center backhaul using thin transponders

Case study: Quantifying the benefits of thin transponders

To quantify the benefits of thin transponders, we performed a network analysis on a fully filled 1,000 km optical link using average sellable price (ASP) and publicly available technical specifications (power consumption, footprint, density, capacity–reach, etc.). Figure 3 shows the area of focus for the analysis, which compared an embedded transponder, a thin transponder and Coherent Routing/IPoDWDM, covering all hardware units inside the dash-lined rectangles.

Figure 3: A detailed view of all three deployment models used in the analysis

As highlighted in Figure 4, thin transponders offer compelling benefits as a third option in addition to embedded transponders and Coherent Routing/IPoDWDM. They offer savings of up to 41% in CAPEX ($/G), up to 36% in power consumption (W/G) and up to 50% in footprint (RU). If we were analyzing vehicles, we could say a thin transponder is a car that gets good gas milage and delivers solid performance.

Figure 4: Benefits of thin transponders over a fully filled 1,000 km optical link

Find out more

Nokia offers a full suite of thin transponders, supported on a wide set of platforms, to address the requirements of any application. Watch our webinar on the pluggable transceiver revolution to learn more about how thin transponders combine key strengths from embedded transponders and Coherent Routing/IPoDWDM to enhance deployment flexibility while providing very compelling economics of reducing CAPEX, power consumption and footprint.