Top 8 Passive Network TAPs for OT and Industrial Networks in 2026

Operational Technology (OT) and Industrial Control System (ICS) environments demand a different standard of network monitoring. Production downtime, safety failures, and compliance breaches are the stakes when visibility tools introduce risk to a live network. Passive network Test Access Points (TAPs) address this directly: they copy traffic without touching the live link, require no power on the optical path, and maintain network continuity even in the event of a complete hardware failure.

Regulatory frameworks including NERC CIP, NIS2, and IEC 62443 increasingly specify passive, out-of-band monitoring as the baseline for critical infrastructure visibility. OT environments are also typically long-lifecycle deployments with legacy speeds alongside modern 100G links, making media flexibility a primary selection criterion. This guide compares seven verified passive TAP vendors across the specifications that matter most in industrial and OT deployments.

Passive TAP Vendors at a Glance

1. Network Critical — Passive Fiber Optical TAPs and SmartNA-XL

Network Critical's passive fiber TAPs deliver zero-latency, powerless optical monitoring across single-mode and multi-mode fiber links from 1G to 100G. Splitting the optical signal at a fixed ratio, these TAPs send a complete copy of full-duplex traffic — including physical layer errors — to connected monitoring tools without touching the live link. There are no active electronics on the optical path, which means a power failure on the TAP has zero impact on network continuity.

The SmartNA-XL extends this passive TAP foundation into a hybrid visibility platform, combining TAP access and packet broker functions in a single 1RU modular chassis. Copper, passive fiber, and bypass TAP modules are hot-swappable across five slots supporting 1G, 10G, and 40G interfaces. This architecture eliminates the need for separate TAP and packet broker hardware — a meaningful advantage in space- and power-constrained OT environments like refinery control rooms or manufacturing floor cabinets.

Where traffic from multiple legacy OT links needs aggregating before reaching a security sensor, the SmartNA-XL's 4:1 aggregation capability allows a single 10G monitoring tool to cover eight 1G links simultaneously. The Drag-n-Vu Graphical User Interface (GUI) handles all filter rule computation automatically, removing the risk of misconfiguration that could introduce monitoring gaps.

For the most demanding environments, the SmartNA-PortPlus HyperCore supports 400G links via 32 QSFP-DD interfaces, making the platform scalable from legacy OT speeds through to hyperscale data center infrastructure within a consistent management framework.

Proven results:

• BP: Passive Fiber Optical TAPs enabled centralized monitoring of IT and OT systems across refinery buildings spanning 10–12 structures, with zero impact on live production traffic.
• Airbus: Network TAPs maintained 100% packet capture across aircraft systems test rigs, enabling Airbus to complete first-flight test objectives on schedule while resolving inherent limitations of in-house Commercial Off-The-Shelf (COTS) switches.
• Vodafone: SmartNA-XL hybrid TAPs aggregated multi-generation copper and fiber links into a unified monitoring view, achieving 100% accurate traffic visibility on key links and reducing customer churn rates.

2. Garland Technology — Passive Fiber TAPs and SelectTAP

Garland Technology manufactures a comprehensive range of passive fiber TAPs specifically validated for OT and ICS deployments. Their passive fiber portfolio covers multi-mode (OM1 through OM5) and single-mode (OS1/OS2) fiber at speeds from 1G to 400G, with portable and high-density 1U chassis options available. The 1U SelectTAP modular chassis supports speeds up to 800G and accepts mixed-speed TAP modules, accommodating environments where legacy 1G OT links coexist with modern 100G backbone connections.

Garland is the only vendor in this list with explicit OT product labeling and a dedicated Dragos platform integration, enabling passive TAP access to feed directly into ICS threat detection. Their hardware Data Diode enforces unidirectional traffic flow from Switch Port Analyzer (SPAN) ports to monitoring tools, providing a physical security enforcement layer suited to air-gapped OT segments. All Garland TAPs carry no IP or MAC address and cannot be remotely accessed or hacked.

Passive fiber TAPs are non-powered and fully transparent. Traffic continues to flow through the live link even if the TAP loses power entirely. High-density 1U chassis accommodate 16 to 24 TAP modules, providing OT network operators with flexible coverage across multiple ICS zones from a single rack unit.

3. Profitap — MOD-TAP and POF-TAP

Profitap's passive fiber TAP portfolio addresses both fixed infrastructure and field deployment requirements. The MOD-TAP modular chassis accepts up to 24 passive fiber TAP modules in a single 1U housing, supporting speeds from 100 Mbps to 400G across LC, SC, MTP, and BiDi fiber types. All Profitap passive fiber TAPs carry a 10-year warranty — meaningful in OT deployments where hardware refresh cycles are measured in decades rather than years.

For environments running Plastic Optical Fiber (POF) — common in automotive and older industrial Ethernet segments — the Profitap POF-TAP is the only purpose-built passive solution in this list. It duplicates and converts the POF signal to a full-duplex 10/100 UTP output with no added latency, enabling legacy industrial networks to feed modern monitoring tools without infrastructure changes.

Profitap passive fiber TAPs carry no IP address, have no management interface, and are fully invisible on the network. Monitoring ports are optically isolated from the live link, acting as a data diode and preventing any signal injection from the tool side. Portable variants support rapid field deployment for temporary monitoring of remote OT assets.

4. Cubro Network Visibility — OptoSlim TAP Series

Cubro's OptoSlim series offers passive optical TAPs in a 1/3RU stackable form factor, supporting every speed from 10 Mbps to 400G across single-mode (1310/1550 nm) and multi-mode (850/1300 nm) fiber. Every Cubro TAP is individually inspected under a precision microscope after assembly, with insertion loss measured and documented for each unit shipped — a level of per-unit quality control that is directly relevant to OT environments where a marginal light budget can determine whether a TAP is deployable on a given link.

Cubro TAPs are completely protocol-agnostic and bitrate-independent. This makes them compatible with legacy industrial protocols running on older fiber infrastructure, as well as modern OT communication standards. The OptoSlim form factor allows up to three TAP units to be rack-mounted in a single 1U space, providing high port density without requiring a modular chassis.

The Cubro EX5-3 Network Packet Broker (NPB) complements the passive TAP range for OT deployments needing aggregation. It provides 48 native RJ45 copper ports at 10M/100M/1G alongside four SFP+ interfaces — directly suited to environments where fiber-based security tools need access to copper OT infrastructure. Cubro also publishes specific OT security positioning, noting that their TAPs eliminate blind spots from unreliable OT switch mirroring without impacting production traffic.

5. Niagara Networks — 3225 Passive Modular Fiber TAP

The Niagara 3225 is a fully passive modular fiber TAP platform in a 1U chassis, supporting up to 35 TAP links via 24 single-width or 12 double-width snap-in modules. Operating at the photonic level, the 3225 requires no power, has no electronics, no IP address, and no management interface. It cannot be remotely accessed or hacked — a hard security guarantee that matters in air-gapped OT segments where the TAP itself must not introduce an attack surface.

Modules support LC and MPO connectors across a range of split ratios, with transparency to all speeds up to 400G. The platform is protocol-agnostic, making it compatible with both legacy ICS traffic and modern Ethernet standards traversing the same fiber infrastructure. Installation is plug-and-play with no configuration required, which reduces deployment time on remote OT sites where specialist networking expertise may not be available on-site.

Niagara's broader portfolio integrates passive TAP outputs with advanced packet broker platforms including the 3808E, a carrier-grade hybrid bypass switch with active TAP and packet broker functionality for environments requiring both passive monitoring and inline security tool deployment on the same platform.

6. Gigamon — G-TAP M Series

Gigamon's G-TAP M Series provides passive optical TAPs designed for enterprise and carrier environments, with unidirectional data flow from network to monitoring tools enforced at the hardware level. This physical unidirectionality prevents any signal injection from the monitoring side — relevant in OT environments where the monitoring infrastructure itself can represent an attack vector.

For applications requiring the highest assurance — including mission-critical OT segments — Gigamon offers G-TAP M Series Unidirectional Taps as a purpose-built variant. Active alternatives in the G-TAP A Series 2 add battery backup and fail-to-wire capability for copper links that cannot be tapped passively, and can be managed through CLI or GigaVUE-FM fabric manager for environments with centralized visibility management requirements.

The G-TAP range integrates natively with Gigamon's GigaVUE Deep Observability Pipeline, which provides aggregation, filtering, SSL/TLS decryption, and distribution for downstream security and analytics tools. Organizations already operating the GigaVUE platform will find the G-TAP M Series a natural access layer extension.

7. Keysight Technologies — Flex Tap II and Flex Tap VHD

Keysight's Flex Tap II is a fully modular, 100% passive fiber TAP supporting speeds from 1G to 400G in both single-mode and multi-mode fiber. Up to 24 Flex Tap II modules deploy in a single 1U chassis, with split ratios available from 50/50 through to 90/10 — giving OT teams control over how much optical power is allocated to the monitoring path versus the live link. The Flex Tap VHD chassis extends this to 36 TAPs in 1U, the highest density passive TAP chassis available from any vendor in this list.

Single-mode Flex Taps are multi-speed and tested across the full 1G-to-400G range at wavelengths between 1260–1340 nm and 1550 nm, validated using Keysight's own test and measurement equipment. The Flex Tap Secure+ variant adds an optical diode that prevents any light from being injected back into the live link from the monitoring port — providing an additional security layer for sensitive OT or government deployments.

Keysight holds thousands of Flex Tap units in stock for rapid shipment, which is an operational advantage in OT environments where monitoring gaps need to be closed quickly following network changes or incident response.

How to Choose a Passive Network TAP for OT and Industrial Environments

Understand Your Fiber Infrastructure First

Identify whether your OT links run single-mode, multi-mode, or legacy fiber types such as POF before selecting a TAP. Single-mode fiber supports longer runs at higher speeds. Multi-mode is common in shorter campus or building interconnects. POF appears in automotive and legacy industrial Ethernet segments and requires a specialist TAP — only Profitap offers a purpose-built passive solution for this media type in this list.

Match the TAP to Your Light Budget

Every passive optical TAP introduces insertion loss on the live link. Your loss budget — the difference between available optical power and the minimum required at the receiver — determines whether a given split ratio is deployable on a specific link. Select split ratios accordingly: 70/30 or 80/20 preserves more signal on the live link, while 50/50 provides a stronger copy to monitoring tools. Vendors including Keysight and Cubro provide insertion loss data per unit.

Evaluate Form Factor Against Site Constraints

OT environments often impose physical constraints that data center deployments do not. Consider:

• DIN rail mounting requirements in control cabinets (check vendor options)
• Rack space — high-density chassis from Keysight (36 TAPs/1U), Niagara (35 links/1U), and Garland (24 modules/1U) minimize footprint
• Portable TAPs for temporary monitoring of remote assets (Profitap offers the most complete portable range)
• Powerless passive fiber TAPs for locations with limited or unreliable power supply

Consider Whether You Need Aggregation Downstream

A passive fiber TAP provides a single copy of traffic from one link to one monitoring tool. If your OT security deployment requires traffic from multiple tap points to reach a single sensor, you'll need aggregation. Network Critical's SmartNA-XL combines passive TAP modules and packet broker aggregation in a single hybrid chassis — eliminating a separate device in the monitoring stack and reducing rack space, power draw, and cabling complexity.

Check Compliance Alignment

NERC CIP, NIS2, and IEC 62443 each reference continuous, non-intrusive network monitoring as a baseline security control. Confirm that your chosen TAP vendor can supply documentation supporting compliance evidence — some vendors, including Garland and Network Critical, produce compliance-specific resources and have reference customers in regulated critical infrastructure sectors.

Assess Vendor Longevity and Support

OT hardware lifecycles commonly run 10–20 years. Choose vendors with demonstrated stability, support programs, and a track record in industrial deployments. Network Critical has been serving industrial clients including BP and Airbus for over 25 years. Profitap backs its passive TAPs with a 10-year warranty. Garland manufactures and tests all TAPs in the USA with 12-month standard support included.

Frequently Asked Questions

What Is a Passive Network TAP and How Does It Differ From a SPAN Port?

A passive network TAP is a hardware device that splits an optical signal on a live fiber link, sending a copy to monitoring tools without any active electronics on the signal path. A Switch Port Analyzer (SPAN) port is a software feature on a managed switch that mirrors traffic to a monitoring port. TAPs capture 100% of traffic including physical layer errors, introduce no latency, and have no impact on network performance. SPAN ports can drop packets under load, are limited by switch processing capacity, and can be misconfigured. In OT environments where availability and data fidelity are critical, passive network TAPs are the preferred standard.

Do Passive Fiber TAPs Work With Legacy OT Protocols?

Yes. Passive fiber TAPs are protocol-agnostic — they operate at the physical layer by splitting light, with no awareness of the traffic content. They work with any protocol traversing the fiber link, including legacy OT protocols such as Modbus, PROFINET, EtherNet/IP, and DNP3, as well as modern industrial Ethernet standards. The TAP simply delivers an exact optical copy of whatever is on the wire.

Can a Passive TAP Bring Down My OT Network If It Fails?

A properly designed passive fiber TAP cannot bring down the live link. Because there are no active electronics on the optical path, a complete hardware failure — including total power loss — leaves the live link unaffected. The two network endpoints continue to communicate through the TAP's pass-through path as if the TAP were not present. This fail-safe behavior is a core requirement for any TAP deployed in mission-critical OT environments.

How Many Monitoring Tools Can a Single Passive TAP Feed?

A standard passive TAP provides one copy of each traffic direction to one monitoring tool. To feed multiple tools from the same link, you need either a regeneration TAP (which amplifies and replicates the signal to multiple outputs) or a network packet broker downstream that distributes traffic across tool ports. For OT deployments feeding multiple security sensors — such as an Intrusion Detection System (IDS), a flow analyzer, and an asset discovery platform simultaneously — a hybrid TAP and packet broker platform such as the Network Critical SmartNA-XL is a more efficient architecture than chaining multiple devices.

What Regulations Require Passive Network Monitoring in OT Environments?

NERC CIP, NIS2, and IEC 62443 all reference continuous, non-intrusive network monitoring as a baseline security control. NERC CIP-007 specifically mandates monitoring of electronic access to critical cyber assets. Passive TAPs satisfy these requirements by providing complete, unaltered traffic visibility without introducing risk to the monitored network. Many critical infrastructure operators use passive TAP deployments as audit evidence for regulatory assessments.

Build Your OT Visibility Foundation With Network Critical

Choosing the wrong TAP in an OT environment is not a configuration problem — it is a production risk. The right passive TAP delivers complete, lossless traffic visibility without touching the live network, and scales cleanly as monitoring requirements evolve.

Network Critical's passive fiber TAPs and hybrid TAP and packet broker platform address the full OT visibility stack: from powerless optical access on individual links through to multi-link aggregation, filtering, and tool distribution in a single modular chassis. With proven deployments at BP, Airbus, and Vodafone, and over 25 years serving regulated, mission-critical industries, Network Critical brings the depth of experience that OT visibility demands.

To discuss your OT monitoring architecture or request a free network audit, speak to the Network Critical team.