Technical7 min read

Fibre Connectivity for Data Centres: Dark Fibre, Lit Services, and Cross-Connect Economics

How data centre connectivity works. Covers dark fibre versus lit services, carrier selection, cross-connect pricing, and the economics of interconnection.

Connectivity Defines a Data Centre's Value

A data centre without connectivity is a warehouse with backup generators. The density and diversity of network interconnection at a facility determines its commercial value, tenant retention, and competitive position. Equinix generates over $2.5 billion annually from interconnection services alone — more than many entire data centre companies generate in total revenue.

Dark Fibre vs. Lit Services

**Dark fibre:** Unlit optical fibre leased from a fibre owner. The customer provides their own optical transceivers and networking equipment to "light" the fibre. The customer controls the protocol, wavelength, and capacity.

  • -Monthly cost: $500-3,000/mile/strand pair (depending on market and route density)
  • -Typical lease term: 5-20 years, sometimes with indefeasible right of use (IRU) for the full fibre life
  • -Capital cost (customer-provided optics): $2,000-15,000 per end depending on speed and distance
  • -Advantage: Full control over capacity, protocol, and encryption. Scalable by upgrading optics without changing fibre.
  • -Disadvantage: Customer responsible for all maintenance, monitoring, and fault isolation.

**Lit services (wavelength/Ethernet):** The carrier provides a managed connection over their fibre network. The customer receives a defined bandwidth service (1 GbE, 10 GbE, 100 GbE, 400 GbE).

  • -Monthly cost: $300-1,500/Gbps/month (varies by distance, term, and market)
  • -Typical 10 GbE metro connection: $1,500-4,000/month
  • -Typical 100 GbE metro connection: $5,000-15,000/month
  • -Advantage: Managed service with SLA. Provider handles fault detection, maintenance, and repair.
  • -Disadvantage: Less control, potentially higher cost at scale, provider dependency.

**Decision framework:** - Under 10 Gbps: Lit services (dark fibre overhead not justified) - 10-100 Gbps: Either model works; compare total cost of ownership - 100+ Gbps: Dark fibre almost always more economical - Multi-site metro network: Dark fibre ring with customer-owned DWDM equipment

Cross-Connect Economics

Cross-connects are physical cable connections between two tenants (or between a tenant and a carrier) within the same data centre. They are the atomic unit of data centre interconnection.

**Pricing:** - Single-mode fibre (SMF) cross-connect: $200-350/month - Multi-mode fibre (MMF) cross-connect: $150-300/month - Copper (Cat6/Cat6a) cross-connect: $100-200/month - Coaxial: $100-150/month

**Revenue significance:** - A large colocation facility may have 5,000-20,000 active cross-connects - At an average of $250/month: $1.25M-5M/month in cross-connect revenue - Gross margin on cross-connects: 85-95% (the physical cable costs $50-200 to install) - Cross-connects are the highest-margin product in the data centre business

**Customer perspective:** Cross-connects are non-discretionary once established — disconnecting a cross-connect disrupts a live network path. This creates extremely high retention (churn below 2% annually) and gives providers significant pricing power. Operators like Equinix have raised cross-connect prices 3-5% annually for over a decade with minimal customer attrition.

**Alternatives to provider cross-connects:** - **Virtual cross-connects:** Software-defined interconnection (Equinix Fabric, Megaport, PacketFabric) at $0.02-0.05/Mbps/month - **Meet-me room patching:** Some facilities allow customers to install their own patch cables in the MMR - **Campus cross-connects:** Connections between buildings on the same campus, typically at 2-3x the in-building price

Carrier Selection

**Tier 1 carriers (global backbone):** Lumen (CenturyLink), Zayo, Cogent, GTT, NTT, Telia — these operate the backbone networks that connect data centres to the global internet and to each other. Transit pricing: $0.30-1.50/Mbps/month at scale.

**Regional carriers:** Crown Castle (fibre), Uniti Group, FirstLight, Windstream — provide metro and regional fibre connectivity. Often lower cost than Tier 1 for intra-market routes.

**Carrier-neutral interconnection platforms:** Equinix Fabric, Megaport, PacketFabric, Console Connect — software-defined interconnection enabling virtual connections between any participants on the platform, across data centres and geographies.

**Selection criteria:** - **Diversity:** Minimum two physically diverse fibre paths to avoid single point of failure - **On-net presence:** Carriers already present in your data centre avoid the cost and delay of new fibre builds - **SLA terms:** Mean time to repair (MTTR) commitments of 4 hours or less for critical circuits - **Scalability:** Ability to upgrade bandwidth without new fibre construction - **Pricing model:** Commit-based (lower unit cost, volume commitment) versus on-demand (higher unit cost, flexibility)

Evaluating Facility Connectivity

When assessing a data centre for connectivity quality, focus on:

1. **Number of on-net carriers:** 30+ indicates a well-connected facility; under 10 is a warning sign 2. **Carrier diversity:** Are the carriers on diverse fibre routes, or do they all enter through the same conduit? 3. **Meet-me room capacity:** Is there physical space for additional carriers to enter? 4. **Internet Exchange Points:** Is there an IXP present or adjacent? IXP presence dramatically improves peering options and reduces transit costs. 5. **Cloud on-ramps:** Direct connections to AWS Direct Connect, Azure ExpressRoute, and Google Cloud Interconnect reduce cloud networking costs by 30-60% versus internet transit.

Browse facilities by connectivity density on our facility directory, or use the Score Tool to assess connectivity at any address.

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