Photonic Switching Capacity Calculator

Gross per wavelength (Gbps) = Symbol Rate (GBaud) × Bits per Symbol

Gross per fiber (Gbps) = Gross per wavelength × Wavelengths per fiber

Total gross (Gbps) = Gross per fiber × Fibers × Spatial factor

Net payload (Gbps) = Total gross × (1 − FEC%/100) × (Util%/100) × (1 − Redundancy%/100)

Effective switching (Gbps) = Net payload × (2 for full duplex, else 1)

1. Enter wavelength count and per-wavelength symbol rate.
2. Select bits per symbol for your modulation plan.
3. Set fiber links and any spatial multiplier for SDM.
4. Apply FEC overhead, utilization, and redundancy reserve targets.
5. Set port count to estimate per-port effective bandwidth.
6. Click Calculate, then export CSV or PDF.

1) Capacity planning for optical switching

Photonic switching capacity is a practical KPI for large builds where fiber routes, site offices, and equipment rooms must be sized early. This calculator estimates throughput from wavelength count, symbol rate, and modulation efficiency, then applies FEC overhead, utilization target, and redundancy reserve. The result supports budgeting for transponders, cross‑connect capacity, and port allocation across the switching fabric. It helps coordinate civil, power, and network teams on scope.

2) Input data you should verify

Start with the DWDM plan: common channel counts are 40–96 per fiber, depending on spacing and spectrum policy. Symbol rate is set by optics and the line system, while bits per symbol reflect the modulation format. Fiber links should match route diversity. Use the spatial factor only when multi‑core or multi‑mode transport is planned.

3) Interpreting gross, net, and effective results

Gross capacity is the theoretical line rate. Net payload reduces that number by overheads and reserves that represent real constraints. FEC overhead often ranges from 15% to 25% in coherent deployments, while utilization targets of 60% to 80% preserve headroom for bursts and growth. Redundancy reserve reflects failover paths and maintenance.

4) Construction use cases and sizing patterns

In campus builds, backbone trunks may be modest in fiber count but high in wavelength use. In industrial or data‑center construction, parallel fibers and higher modulation may reduce duct congestion and installation labor. Per‑port effective capacity helps validate whether a planned chassis can sustain demand without severe oversubscription.

5) Reporting and handover documentation

CSV exports support side‑by‑side option comparison, while PDF output fits procurement packs and commissioning reports. Save assumptions with drawings and bill‑of‑materials notes so reviewers can reproduce results. Treat this estimate as a planning model and confirm final parameters with vendor datasheets, link budgets, and acceptance tests.

1) What does “effective switching capacity” represent?

It is the net payload capacity after FEC, utilization, and redundancy factors, scaled by directionality. It helps compare design options using a consistent planning basis.

2) Why is FEC overhead subtracted from capacity?

Forward error correction adds parity and coding data to improve link robustness. That extra information consumes line rate, so payload throughput is lower than gross capacity.

3) How do I choose bits per symbol?

Bits per symbol depends on modulation format and achievable optical signal quality. Higher values increase gross capacity but may reduce reach or margin. Use vendor targets for your reach and fiber quality.

4) What is a good utilization target for construction projects?

Many planners use 60% to 80% to preserve headroom for bursts, commissioning activity, and growth. Higher targets can be risky when traffic is unpredictable or when failover paths share resources.

5) When should I use the spatial factor?

Use it only when multiple spatial channels exist per route, such as multi‑core fiber or multi‑mode transport. For standard single‑mode fiber designs, keep the spatial factor at 1.

6) Why include a redundancy reserve percentage?

Reserve accounts for protected services, planned diversions, maintenance windows, and future expansion. It prevents designs that look sufficient on paper but fail during outages or growth.

7) Can I use this output for final procurement?

Use it for early sizing and option screening. For procurement, confirm optical line constraints, channel plans, link budgets, and equipment specifications, then update assumptions to match accepted vendor designs.