How to Make an Existing Fiber Optic Connection Quantum-Safe

Quantum computers pose a growing threat to existing network security. While classical encryption is still sufficient today, powerful quantum systems will be able to break common encryption methods in the near future. For organizations working with sensitive data over fiber optic connections, the question is not whether you need to take action, but when. This guide walks you through step by step how to make an existing fiber optic connection quantum-safe, without having to rebuild your entire network.

The good news: an existing fiber optic infrastructure is an excellent foundation for quantum-safe security. Fiber is inherently difficult to tap without detection, and with the right encryption layer on top, you can prepare the connection for tomorrow’s threats. Follow the steps below in order for a structured and secure migration.

What you need before the migration

A successful migration to quantum-safe fiber optic security does not start with technology, but with preparation. Without a clear starting point, you risk creating security gaps or making choices that later prove unscalable. Make sure the following elements are in order before you begin:

• Network topology documentation: an up-to-date overview of your fiber optic infrastructure, including nodes, routers, and switches
• Inventory of active connections: which connections are business-critical and what data flows over them?
• Classification of sensitive data: identify which data streams have priority in the migration
• Insight into current encryption protocols: know which encryption is currently active at layer 1, 2, or higher
• Involvement of the right stakeholders: ensure IT security, network management, and management are aligned
• Compatible hardware: check whether existing equipment supports firmware updates or extensions for post-quantum cryptography

Have these points been checked off? Then you have a solid starting point for the steps that follow. If any information is still missing, map it out first before proceeding.

Map your current network

Before you change anything about your network security, you need to know exactly what you have. A thorough inventory prevents surprises during implementation and helps you set priorities. Think of your optical infrastructure as a whole: from the physical fiber optic routes to the active equipment that processes data.

1. Create a complete overview of all fiber optic connections, including length, fiber type (single-mode or multi-mode), and connectors used.
2. Document which equipment is connected to the connections: routers, switches, transponders, and multiplexers.
3. Identify the current security layers: where is encryption currently applied, at which OSI level, and with which protocol?
4. Map the high-risk connections: which routes carry sensitive or business-critical data?
5. Note where physical access to the fiber is possible, as these are the vulnerable points for eavesdropping.

After this step, you have a clear picture of your network and know which connections need to be made quantum-safe first. Use this overview as a guide for all subsequent decisions.

Choose the right quantum-safe security method

There are two main approaches to securing a fiber optic connection against quantum threats. The choice depends on your infrastructure, budget, and the desired level of security. Understand both options well before making a decision.

Post-quantum cryptography (PQC)

Post-quantum cryptography replaces classical encryption algorithms with mathematically complex alternatives that even powerful quantum computers cannot easily break. PQC operates at the software level and is therefore relatively easy to implement on existing hardware via firmware updates. This makes it a practical choice for organizations that want to act quickly without major investments in new equipment. Standards for PQC matured further in 2026, with international certification of multiple algorithms.

Quantum Key Distribution (QKD)

QKD uses the physical properties of light to distribute encryption keys. Any attempt to intercept the key is measurable, because it disturbs the quantum state of the photons. This theoretically offers the highest level of security, but requires specialized hardware and is currently more expensive and complex to manage. QKD is particularly relevant for organizations with extremely high security requirements, such as critical infrastructure or government institutions.

For most professional organizations, a combination of PQC at higher network layers and layer-1/layer-2 encryption on the fiber is the most practical approach. Want to know which approach suits your situation? Our security solutions for quantum threats give you a good starting point.

Implement the encryption layer on the fiber

With the choice of a security method made, it is time for the actual implementation. Encryption at layer 1 or layer 2 of the fiber optic connection provides the most fundamental protection, independent of the higher network traffic. Also check our overview of available encryption solutions for specific product options.

1. Select encryption equipment that is compatible with your existing fiber optic infrastructure and supports the chosen security method.
2. Install the encryption units at both ends of the connection to be secured, preferably in a secure server room or rack.
3. Configure the key management infrastructure: set up how keys are generated, distributed, and renewed.
4. Run a test connection over a non-production environment to validate the configuration before going live.
5. Enable encryption in phases on production connections, starting with the least critical routes.
6. Document all configurations, key management processes, and equipment settings for future management.

Note: with layer-1 encryption, all traffic over the connection is encrypted regardless of the protocol above it. This is powerful, but also requires that both sides of the connection have identical hardware and configuration. Verify this before going live.

Validate and monitor the secured connection

An implemented encryption layer is only reliable when you can demonstrate that it works correctly and that you detect anomalies in a timely manner. Validation and continuous monitoring are not optional steps, but an essential part of quantum-safe network security. Real-time fiber optic monitoring helps you maintain continuous insight into the state of your connection.

1. Perform a penetration test on the secured connection to verify that the encryption has been correctly implemented.
2. Set up monitoring on the encryption equipment: generate alerts for key errors, connection interruptions, or suspicious activity.
3. Regularly check that key rotation is taking place as configured and that certificates have not expired.
4. Establish a baseline of normal network behavior so that anomalies are quickly noticed.
5. Schedule periodic audits of the encryption configuration, at least once a year or after major changes to the infrastructure.

After validation, you know that the connection is genuinely configured to be quantum-safe. Monitoring ensures it stays that way. Preferably use a centralized system that monitors multiple connections simultaneously.

Common problems and how to solve them

Even with a careful approach, problems can arise during or after implementation. Below are the most common challenges and how to address them.

Latency increases after enabling encryption

Encryption at layer 1 or 2 always adds a small processing delay. If latency is higher than expected, check whether the encryption hardware has sufficient processing capacity for the data volume on the connection. Outdated or undersized equipment is often the cause. Upgrade the hardware or adjust the encryption settings to reduce the load.

Key management does not synchronize correctly

A key mismatch between both sides of the connection causes the encryption to fail or the connection to refuse to establish. Check that time synchronization (NTP) is correctly configured on both devices, as key distribution is often time-sensitive. Also check that the firmware on both devices is on the same version.

Existing equipment does not support PQC updates

Not all hardware can be updated via firmware to post-quantum algorithms. In that case, there are two options: add an external encryption appliance placed in front of the existing equipment, or replace the hardware with a model that does support PQC. Plan this as part of your regular replacement cycle.

Unexpected connection outage after implementation

Outages immediately after enabling encryption often point to a configuration error on one of the sides. Temporarily disable the encryption to confirm that the base connection is stable, then go through the configuration step by step again. Always make sure you have a rollback procedure ready before applying changes in a production environment.

Can’t figure it out or want to discuss the approach that best fits your network? We are happy to help you with protecting sensitive data over your fiber optic infrastructure.