Pacific Crossing-1 (PC-1)

Pacific Crossing-1 (PC-1) is a 21,000 km submarine cable between the United States and Japan, first lit for service in 2000 and fully commissioned in 2001. It is one of the oldest trans-Pacific cables still in commercial operation. Its four landings sit at Grover Beach in California, Harbour Point (Mukilteo) in Washington, Shima in Japan, and Ajigaura also in Japan. PC-1 predates the iPhone, it predates Gmail, and it predates every other cable we have covered on this site. It is over a quarter-century old.

When PC-1 lit, its 8.4 Tbps design capacity was state of the art. In 2026 that number is modest — APRICOT, commissioned 25 years later, carries 35 times as much capacity across a similar length. But PC-1's design life was 25 years, and by every reasonable measure, the cable is now at the threshold of its planned retirement. What our measurements show, though, is that the cable is not just still running — it is still running at the physics floor.

115.7 ms across a quarter-century

Our monitor measures PC-1 from Grover Beach in California toward a Japanese target. Over 30 days we collected 42 samples. The data is extraordinary:

Every single sample across 30 days falls within a 9 ms window. The standard deviation of 2.88 ms is tiny — the distribution is so tight that consecutive measurements often differ by less than 0.1 ms. This is the signature of a cable operating cleanly, with no faults, no capacity pressure, and no routing changes disrupting its baseline performance.

The great-circle distance from Grover Beach (San Luis Obispo County, California) to Shima (Mie Prefecture, Japan) is about 8,500 km. Light in submarine fibre makes that round-trip in a theoretical minimum of 83.1 ms. We measure 115.5 ms — about 1.39× the great-circle floor. For a 25-year-old submarine cable delivering that close to the physics limit of modern fibre, this is remarkable.

Put differently: PC-1's fibre optic path is roughly 11,800 km long (computed from the measured RTT). That is about 40% longer than the great-circle distance, which is typical for trans-Pacific cables — they curve northward to take advantage of shallower shelf water and to connect through intermediate landings, rather than crossing at the deepest, shortest geodesic.

A 25-year design life reaching its end

Submarine cables are designed to last 25 years. This is a deliberate engineering target that shapes every aspect of the system:

• The steel and polymer armour that wraps each cable is rated for 25 years of sustained pressure, salt water exposure, and occasional abrasion from seafloor movement.
• The repeater amplifiers (erbium-doped fibre amplifiers, EDFAs, placed every ~80 km along the cable body) are built to run continuously for that period without maintenance. Each is a titanium pressure vessel containing a sealed optical pump laser and passive optical components.
• The power feed system — high-voltage DC electricity sent through the cable body to power the repeaters — is designed to maintain stable current through the full design life despite minor insulation degradation.
• The fibre itself is the part that actually lasts beyond 25 years. Submarine-grade optical fibre has no known wear mechanism under normal operating conditions. It can carry signal indefinitely if the surrounding cable body and repeaters hold up.

PC-1 lit in 2000–2001. That puts the cable in its 25th or 26th year of operation. By the original design schedule, it is now in its final commissioned year. Our measurements confirm the cable is still delivering close to physics-floor performance, which means no repeater chain failures have occurred that would have caused the latency to spike, and the cable body has retained sufficient optical continuity for clean long-haul signal propagation.

Four landings, two countries

Two landings at each end gives PC-1 diversity in its continental backhaul — a US-originating packet can route via either the Central California coast (Grover Beach) or the Pacific Northwest (Harbour Point), depending on which landing has better connectivity to the specific source network. On the Japanese side, Shima is on the Pacific coast of central Japan, and Ajigaura is further north — giving Tokyo-area traffic a shorter intra-Japan backhaul to Ajigaura while Osaka and western Japan route through Shima.

This two-landings-per-continent architecture is still used in some modern cables (JUPITER also lands at multiple points on each coast), but it was relatively novel in 2000. Many earlier trans-Pacific cables had single landings on each side, which meant the cable's usefulness depended entirely on terrestrial backhaul to reach wherever the traffic actually needed to go.

8.4 Tbps in the year 2000

PC-1's original 8.4 Tbps design capacity was achieved with four fibre pairs running 64 wavelengths each at 33 Gbps per wavelength. Those numbers reflected the absolute state of the art in 2000 — 10 Gbps wavelengths were just becoming commercially available, and 64-channel DWDM was pushing the limits of available equipment.

Today's cables achieve the same capacity on a single fibre pair using current-generation coherent modulation — 80 wavelengths at 200 Gbps each = 16 Tbps per pair. Submarine fibre has not fundamentally changed in 25 years; the transponders and their modulation schemes have. PC-1's original specs reflect the 2000-era transponder limits; if the cable's electronics have been refreshed since commissioning (as is typical every 5–7 years), its current capacity is substantially higher than the original specification.

Even at its 2000-era rated capacity, PC-1 was built to serve 2000-era demand. The internet's backbone traffic volumes have grown by factors of many thousands since then. PC-1's relevance today is not raw capacity — it is the existence of a working cable body that has outlasted its rated life and continues to deliver clean latency performance.

What our data proves

• PC-1 delivers 115.5 ms minimum Grover Beach → Japan, 1.39× the great-circle physics floor. Twenty-five years after commissioning, the cable is operating at close to theoretical performance.
• Standard deviation of 2.88 ms across 42 samples is among the tightest we have measured. The baseline is stable; the cable is not under capacity pressure or suffering from repeater degradation.
• Physical infrastructure outlasts its rated design life. PC-1 is past its 25-year planned lifetime and still producing publishable telemetry. Submarine cables, when properly built, age gracefully.

PC-1 is a quiet landmark in trans-Pacific connectivity. It was commissioned before the current generation of cable engineers entered the industry. It has carried traffic through every major shift in internet architecture of the last 25 years. And our 2026 measurements show it is still functioning essentially as designed. When PC-1 is eventually retired, it will be because of economic obsolescence — newer cables offer much more capacity at lower cost — not because of any failure of the physical infrastructure.

Try it yourself

Live data on the PC-1 cable page. For contrast see JUPITER (2020 trans-Pacific hyperscaler), APRICOT (2025 intra-Asian), and BIFROST (2025 southern-corridor Asia-Americas).